i havn't personally but I've heard people who have, or they just remove just the cushions

but what i'm thinking is poke the hole, reroute vacuums, and put the button in, probably with a little glue in the edges but take this with a grain of salt

honestly i probably have enough parts sitting in storage to actually try it..

i know someone who put 500e seats in his 300ce though i'll shoot him a pm if you want later
and if its just the seat bottom technically they should just be interchangeable