Just a note from past Yok BD experience.
anyone looking to release or make a 3mm or thicker chassis...
milled out pockets are a must for the BD...
the car does not like to sit high on a straight 3mm lower deck, the roll centers just don't get right.
I've used two different 3mm chassis and the car just didn't feel right at all, but once I put the car back down to the intended Yok (hard chassis) chassis it got all the grip back.
a 3mm or 3.5mm top deck would be great but the belt path needs to have a pocket also, belt will rub and where down very quickly without it. I always wanted to see someone release a 3.5 top deck with the pockets milled on the underside to keep the center of gravity as low as possible and assist the flex with a key-in effect.
just a few thoughts....anyone listening