I have been using a second stem system for years, handlebar bracket is lower that way, that was the primary reason that I used that. I have that on several bikes. And have the interrupter levers on the regular bars.
If however you have a smaller sized frame or your bars are much lower, this could put your bag too close to the tire or fender, so might have to do some measuring first if that might be an issue. My frame sizes in the photos range from 58 to 61cm effective seattube length, that is tall enough that on some bikes I have room for a headlamp below the bar bag.
On one of these bikes, I initially had a short piece of PVC pipe in the second stem. That pipe broke and fortunately I was close to home when it did. I now would only recommend a piece of handlebar that was cut for the purpose, or a solid piece of metal.
I did not originate this idea, saw a photo of a bike setup this way over a decade ago, but since then I have mentioned this over a dozen times on this forum.
I like my interrupter brake levers angled downwards like in the photos, if you like your levers angled more forward, that would mean your second stem would have to be a bit longer. I prefer my bar bag to be as close to the steering axis as possible for weight reasons, the further forward the weight is the more that weight in the bar bag can impair handling. So, I try to have just enough room for my fingers (which might have thick gloves in cold weather) between the brake levers and the bag.
On the bike below I used an adjustable stem to get the bag lower. Side note: Notice my parking brake, use an elastic on the brake lever. That is an extra thick hair band.
The bike below has 26 inch wheels, thus more room below the bar bag, I even have a tiny rack mounted on the canti brake posts.
Thorn makes an accessory T bar, but shipping from the UK is pretty expensive these days. Nice thing about that is that it only consumes about an inch of steerer tube, much less than most second stems. But the Thorn one does not angle down like the one that Happy Feet made. They come in two lengths, I have the 55mm.
https://www.sjscycles.co.uk/accessor...n-222-mm-0-deg
Bike below has that T bar, this bike has 26 inch wheels, thus more room below the bar bag.
By using the second stem for the bar bag, that means I have a bit more real estate on the handlebar available for other stuff like a bell and a GPS unit.
