Tires again

We are new to the forum, just got back from a trip during which we blew out what we thought were 6 year old 14 inch marathons which were actually 9 year old marathons on a 2006 2720. They were three years old already when we bought the trailor new.

Want to upgrade to 15 inch load range D as on the tires, thread. Just want to make sure we got it right. I have ordered 2600lb 15X6 wheels, 225-75-15 Load range D marathons and steel valve stems. It is going on a 2720 that will be stored outside with the lift kit. I was not able to get any guidence from trailmanor on wheel width so used the forum advice on 6 inch.

I understand I will have to have my spare tire holder modified. I may have a issue with the fender skirts. Any concerns about this plan other than some people seem to prefer other brands.