What do you do? Inboard of shifter or outboard?
I have an X-Fusion Hilo with the old lever, it doesn't really fit nicely. I'm considering getting the newer lever that you can push any way.
I'm in a similar position - just bought Brand X and it comes with the 1x lever which I have temp mounted on top right side but this is no long term solution. Used to have a Hilo with the push down lever which was ok but not great.
Bontrager Universal lever looks like it might be ok?
I have a HILO SL with the lever that goes any direction, works well. Just mounted in-board of the rear shifter.
Above or below the bar fossy?
I have the 'end of the lever' a little higher than the shift levers, but inwards - so no missing with either. It overlaps the clamps of the Shifters and brakes (SRAM X9 and Guide RS - no combo clamp) It's the straight lever that you can push anyway/up/down and pull - I usually just push inwards. Change the cable and outer for a good lined cable (e.g. Shimano PTFE or Decathlon ones.
It works well. The original cable lasted a year, but it was pants compared to a decent brake cable replacement.
So it's just below the middle of the bar, not above or below.