I agree about contact cement. I've removed that vinyl cover from 4 Vetta saddles, in the past few years, and replaced them with leather covers. I use a spray adhesive to bond the leather to the foam but then use contact cement to bond the leather edges to the plastic seat pan. I use DAP Weldwood contact cement in the small 3 oz bottle. According to DAP it is different from the 'same thing' in the larger metal cans. The nice thing is that there is no mess from overspray since you're using the brush from inside the bottle.

I do clean the seat pan real well - remove all old adhesive, clean with mineral spirits then again with isopropyl alcohol. Apply the cement, wait 15 minutes then carefully press the cover into place. No clamps or wait time required. I've been using these saddles 'in the wild' for several years now, all year long in Pennsylvania, and they're doing just great. I do not let the saddles get wet.

If'n I were you, I'd use the contact cement for your vinyl cover fix. Good luck.