After a month riding on stock bike, my CHANGE is upgraded:
new weight 9.06kg or 20lbs without paddle
my personal new record at 38.3km per hour
upgraded parts: wheels, crankset, seat post, etc
future upgrade: fork to become carbon or titanium, and titanium paddle

9.06kg is a good weight for a folding full sized bike.
I am sure a carbon fork will make it even lighter.
What is the material of the current fork?

aluminium

Oh.. did not notice that they provided an aluminum fork (very uncommon ).
Carbon one will probably only save a little over it, but will be better on how it transmits road buzz.

The ChangeBike is a really good option for someone looking for a full sized bike that takes standard parts.

You seem to be running continental slicks which is amongst the best when it comes to rolling resistance.

From where you are now, I doubt a carbon fork would do much, yes, it will shave few 100g but the thing that slow you down the most is "you". With flat bars, you create loads of drag (air resistance). If you want to be faster, you better spend the money on tucking in stuff like drop bars for better aero. Then once that's done, go for lighter aero wheel that will spin faster easier.
once Drap and Dynamic weight is dealt with you can move to static weight.

Static weight affect mostly climbing a low speed.

sounds like u expect a faster record, which i hope. After the above setup i also lower the t-bar again to the lowest possible and notice the slightly move of CG forward, similar to the feel of my another road bike (not foldable). I just started cycling frequently for five months and still hope to break my records at my age of 54.

yes, if you are doing ~38kph with flat bars, you should get a bit better with a road bike setup.
Age does not matter, your fitness does (which is obviously affected by age). A friend of mine is 15 years older than me and he always destroys me over a 50 to 80k XC ride...

Interesting! I indeed didn’t try to break my own records but every new records were created when another rb trying to pass over me but failed… and agreed age is not a big deal but its to experienced and fit players. And yes i beat a lot tennis friends whom are much younger than me…

There is a downside to using road bars on the Change.
I have one configured w/ road bars as a gravel bike using the newer MTB frame.

It does affect the fold to become not as compact, unless you can arrange/fit your road bars at a height that enables you to turn in after fold and not hit the frame.
If riding and folding compact is what you want, then consider just leaving it as a flat bar.
I use my bike for local group rides as well as touring and headwinds can be beating on me the whole day for days, so I do prefer the road bars for whatever wind hiding it gives.

this is also the reason for me to keep the t-bar, so I can keep moving the folded bike easily with one wheel rolling.

I'd be reluctant to put flat bars on that bike too. Apart from affecting folding and increasing the bike's footprint, unless you're actually riding the in the drop position there's little difference. Personally I find I ride the hoods almost all the time with drops. Also, brakes and shifters become more complicated and much more expensive. Ergonomically I find drops less comfortable than flats too, which can affect both endurance and confidence which both in turn can affect performance. Low flat bars are the way forward, imo unless one intends to actually race against roadbikes and are actually going to use the drop position.

very true to me!

you mean:


when you fold it, doesn't the go around the top tube? if so with modern short reach bar, I cannot how it takes more space than a flat bar. the overall reach between flat and drop should not be too dis-similar.

alternative can be the Surly gravel dop conversion bar

Even when riding with road bikes, if one is cunning and not gentlemanly about it, flat bars are usually fine.
It will involve not taking the pull and maximizing drafting, only launching out at the last moment.
Generally works unless the guys in the ride can punish you really hard by sustaining at the limits where that bit more aero of the drops even is a pack is necessarily.


Personally, I don't like to do it.

Kinda hard to explain in words..

Riding Tales explains and illustrates it well with a photo.
Change Bike: Custom Drop Bar Upgrades — Riding Tales

"

• Although it might be possible for 40mm of spacers to work, the issue lies with the angle of your handlebars. If you have either too many spacers or too much upward angle, then the hoods of the handlebars will hit the rim of the rear wheel when you try to fold it.
  
  "
  
  "
  
  This really isn't a strict requirement by any means, but it is helpful. The goal is to be able to easily slot the hoods of the handlebars through the spokes of the rear wheel so that the bike can be folded compactly.
  
• We found Campagnolo and Fulcrum wheels to be the easiest to use in this regard. The widely spaced spoke pattern gives enough room to easily tuck the hoods through.
  
• Wheels with dense spokes won't work. If there are too many spokes, there is no room for the hoods to tuck in. The bike can still be folded, but it would be a much wider fold where the handlebars can't turn in completely.

Interesting read that I found when re-looking for the Riding Tales webpage.

ChangeBike DF-702 Folding Bike: Three Month Review – Jess in Mannheim (wordpress.com)