71 BUS...can i flip/switch pop-tops for upper bunk?? Canvas for rear bed extension anyone have to pattern?

such a waste of space... i would love an upper bunk...that suicide hammock is just that...lol...would be nice to take another couple camping....is it possible to switch tops?...i was told my roof is not flat like the laters...but couldn't u manipulate foam under cushions to make level??....i know there is a flip down (forward)foot piece that i will need to get...and the support bar holding that

piece...has anyone one this and care to share??

ALSO....i have the bed extension piece you attach to the rear

hatch, but do not have the rear canvas tent cover...anyone know where i can get one?...or at least one to pattern off of.....please advise...thanks