Another.15" trailer tire question

Thanks guys for all of the input. To begin with, I called the dealer where I bought my trailer and asked them their real-world experience with adding 235/80/16 tires and wheels to a trailer specifically like ours. He said there wasn't room for it to happen. I measured the distance between the top of the 15" tires and the bottom of the fender and I felt he was giving me good information.

So ... I did order the Goodyear Endurance 225/75/15s which are 10-ply, E rated and rated to 2830. Boy, just from first impressions they are heavy-duty quality tires! Discount Tire always takes care of us and they did a nice job mounting and balancing them. When I took the old bias ply tires off I noticed they weren't even balanced and we bought the trailer new. I haven't towed with it yet but I'm looking forward to it.

Regarding the Discount warranty program I didn't buy it at the time but they said I could come back in and get it (which I still may). I didn't ask them but I wonder if I had a blow-out are the tires prorated or do you just automatically get a new one no matter how old the tires are? If that is the case I might get it but if they are prorated, and the tires are only $131 each, might not make sense to purchase it.