People ask “what length stem will I need if I fit an h-bar? Can I just use the one I have?” I’d recommend using the same size stem you would use with a normal flat bar if your bike fit is already the way you like it. You may want to stay with what you have and ride for a while to see how it feels. The h-bar is now designed with a shim to pair with an over-sized stem – this is something to consider if you currently run a standard bar diameter.
The main grip position of the H-Bar has the same reach as a normal XC bar.
Here are some hand positions. I’m using a 100mm x 10° stem on a bike with a 23” ETT. I’m 6’. The bar is about level with the seat.
Seated climbing (above) with hands on cross bar and front extension. This is more forward than a normal bar.
Standing climbing with thumbs hooked over cross bar. This is a little forward of a normal bar grip. It feels a bit like riding the hoods of a road bike here.
In the down hill position you grip the wide and rear part of the bar to get weight back and off the front. This position is further back than with a normal bar. It feels like having a very short stem and is harder to endo.
I do not recommend using a longer stem to make this grip position have the same reach as a normal bar. It will make the front positions too far forward and make you less likely to use them. It will also reduce how much you can get your weight back on the down hills.