Since Tesla needed a new sheet after the waterproofing on hers failed in the first big storm, I went ahead and got them both one. Riding Warehouse had a sale on the Amigo Hero ACY Sheets - I liked the extra lightweight for layering (and washing, hey!), they were on sale, and I had a 20% off coupon, so I took the plunge.
a 76 Red for the Porsche
and an 81 blue for the Tesla (a 78 would have been perfect, but room for layering is good!)
Tesla can wear anything, she is always super gentle on her clothes, but I was a bit worried about the no back leg straps for the little destructo - but so far, so good! The tail strap is not removable (Ewwwhh! total design flaw!) but I will swap it out so that I can clean them regularly.
I took Cob Jockey's advice and bought liners and so far, this system has worked really well: a waterproof sheet, and liners as needed. It has dropped down to 8C at night here, and they've been just fine :)