We take care of our own backing as needed. The framer will charge them twice as much to come back out if you are late to getting the job which is usually the case. We include the cost of backing on initial pre-wire and cut all backing in our self's as well as center channel speakers, load bearing walls to have headers when studs are cut. helps that I framed houses for 5 years before I started this work.

I have trained our tech on how to do this and since we build custom boxes all the time the tech's are getting better at carpentry work.

At what point / weight do you do backing?