mstateglfr 

If a road bike with 72mm drop and 28mm tires is compared to a same sized road bike with 77mm drop and the same 28mm tires, assuming saddle height relative to center of bb is the same, then the bike with 77mm drop will have a saddle that is 5mm lower than the bike with 72mm drop.
This is due to the bottom bracket being 5mm lower on one bike.


Probably didn't phrase it well the first time.

canklecat

Ditto, Continental Speed Rides. It's what I use on similar gravel and worse. Good and cheap, a rarity.

Keep the tire pressure down for the gravel. Carry a pump and you can re-inflate a bit as needed when the terrain switches back to pavement. Usually I run 'em around 50-60 psi rear, 40-50 front, for all around stuff since most of our MUP unpaved trails are crushed limestone chat trails, easy to ride even on slick road bike tires. So far, so good with the Speed Rides.

But some stuff is like railroad track ballast, horrible stuff that'll cut some tires to pieces. The toughest tires I've ridden are Michelin Protek Cross Max. If I had to ride lots of rail track ballast or similarly large, sharp gravel, that's what I'd use. I have those tires on my errand bike with spring fork, and occasionally take it for longer bad road conditions.

Well done on the weight loss. Took me 15 years to drop from 205 to 150, but 25 of that came off after summer 2015 when I resumed cycling. Cutting way back on the beer and sugary snacks helped with the weight loss. Riding bikes helped with everything else, from blood pressure to anxiety.

Witterings

Currently have these on my 29er as it's summer and they're brilliant in the summer / dryer weather .... I bought them in the autumn last year and tried them on my gravel bike but they had no grip in mud but will put these on my 29er every summer for mixed use and swap back to something a bit more mud friendly in the wetter winter months.

I'd still rather a wider tyre though of the OP really is doing 20 miles on that sort of gravel on a regular basis.