Peter, I removed the stinky slinky tube off the front and the spare tire of the back...so I too had some holes to fix. I used Marine/Plastic Fiberglass Repair. It's a two part putty, cut off a chunk and kneed until the colors combine...roll into a sausage and stuffed it in. It's sandable and paintable. The color doesn't match perfectly tho. I'm not sure anything would. Perhaps a tiny bit of spot paint
would help. I bought it at Lowe's for less than $5. I also used it on a wood fence when the gate catch screws had stripped out.