Any experience with "offset" q-factor

Okay ...

I'm an inquiring mind.

WHY ARE YOU MIXING CRANK ARMS?

I presume that you are talking about a Hollowtech II (HT2) crankset rather than an Octalink Crankset because the latter use two different Octalink splines.

If properly installed, there is NO offset difference between the left side & the right side crank arms from the centerline of the bike!

If you are missing the left crank arm for ANY Shimano crank, then you can either order a replacement through your LBS (yes, it will be fairly expensive) OR if you need an XT-compatible arm, then you can probably substitute an SLX-or-LX HT2 crank arm cannibalized from a "complete" crankset.

The same is true if you are missing a left Road crank arm for a Shimano crankset -- either order a replacement or cannibalize ("borrow"😉 one from a less expensive Shimano crankset which uses the same type of BB.

Thanks for your input! Yes Hollowtech II

I am considering investing in a "Stages Crank Arm" Power Meter stagescycling.comstagespower modelsOpen ↗

Being on a budget (I guess who isn't), I am exploring buying the XT w/power meter in it and being able to make it work on my CX/road bike. $800 for ultegra crank w/power meter

It will not work the other way - Ultegra arm on XT crank (not enough clearance for power sensing unit) stagescycling.comsupport compatibilityOpen ↗