Hi Larry
I have the seats out now and apart. Like yours, the bottom pads are in need of replacement, but the backs look like new - no shedding, no anything - so I have decided to just order the bottom pads only.
Now that I have taken them apart, I'm not sure how a plastic bag could help? I just ordered two types of canvas & leather stretching pliers from Amazon which I hope will help me get the new leathers stretched correctly. I'll also try your ratchet strap idea. I bought two diameters of noodles, new rings, ring pliers and stainless steel zip ties. Once I get the new bottom pads in and make progress, I'll post some pics.
Thanks
Doug