A few thoughts from my experience with my mid-build.
Have you considered to flip the rear arms the other way around?
That will of course give a shorter wheel base if the chassi length is left unchanged but you will then have all the heavy bits a few mm closer to the rear axle.
Is the 2mm lower shock mountings made to compensate the shocks need to be longer? If the shock is mounted from behind, the lower mount sits a few mm lower due to the anti-squat angle of the arms.
Good luck with everyting!
My mid is a killer and guess your's will be to.
/Mr. Pink