Long time Quarq user here and I wouldn’t use anything else.
Go for a 4iiii then!
I used to use Stages on my bikes (I’m a Shimano guy as well), but I’ve switched to 4iiii since Stages has gone under.. 
1 Like
The 4iiii that came with my XC bike has been totally forgettable. Which is a good thing as it has caused me zero problems or thoughts.
1 Like
Think that leaves you with..
4iiii crank arm
Assioma Pro MX pedals
ROTOR INspider MTB, Shimano edition INspider MTB Shimano® compatible
There are direct to consumer Chinese brands, like Sigeyi but depending on where you are in the world, might be easier to go with one of the above.
1 Like
I descend with right foot forwards and still get some pretty crazy spikes with my left side only pm.
I have 2 Power2Max devices (1 on MTB, 1 on Gravel), just email them for compatability, I’ve found that they are very responsive.
2 Likes
The thing about the MTB is that you tend to need to STAB the power more. I had a left PM and thought it was giving me a low number vs my road bikes, as my right leg is my lead off hitter. I got Assioma dual pedals… they got the same numbers. I resold the pedals because I didn’t like the sloppy bearing on the MX pedals.
I found a 4iiiiiiiiiiiiiii XTR (2-bolt) for $140 a few years ago because XTR went 1-bolt. It’s basically the same weight as a XT or SLX. The three different spindle lengths use the same arms, so don’t be afraid to mix arms. In any case, just get the cheapest one that makes sense.