I did steam my foam on my seats, and it apears that maybe its a design flaw with the lower seat covers, because no matter how much I play taffy machine on cover, the center just wont get tight. Part of the flawy may be that the covers are anchored using the plastic flaps slid under the bolsters, so while you pull, it pulls tight on the bolster, but just pulls them outward. There is no pull to the frame of the seat.

While it may be some due to 40 years of collapsing, cant be the whole thing, cause the original covers were still super tight (though ripped..hehe).

I may put a piece of padding in the center to fill that out a bit.