So every passenger in the 8 crawls out on a cold day with gloves and scarf cause there is no rear heat in the Back. Wife Michelle says no no no. I have to have heat and your gonna give it to me or else!
The problem is that damn spar web. After some analysis, I decided that the center web at the root could take the hole I needed if I encroached into the hole that is already there for the stick controls. Full stick deflection only takes up 75% of the hole that has been provided. So I took a hole saw to it. Pictures below. Remember. This is NOT the spar, it is the spar web. The webs job is to keep the spar separated. By the time the wing loads are transferred here, the shear loads are very minimal. Remember this is experimental and flight testing will determine if the wings will rip off or not. This has neither been tested nor recommended.
Update: This has now been tested and the wings have not come off. I do believe I am the only RV-8 with rear cabin heat. Yipee! My wife love me for it.