I have trailed my boat all over and only have ever had 8in wheels,all been fine.
What has come to mind over many years is that so many factors have an effect on tyre wear that it can not be just one thing ?
Weight in the boat,speed,kind of road surfaces all over europe and many other things have done many things,or not to my tyres.
Had a tyre wear on one side very badly on my trip to Holland, on as long a trip to Denmark it did not do the same thing to the same wheel with a new tyre ?
As the kids say” Whats that about “
Had the use of a new combi with 10in wheels recently, what a pain it was to get the boat off without the boat hitting the ground on exiting the base,so high of the ground and the boat so far forward on a very long trolly that I will not be having that combi next time round.
10in wheels are very good and must be better than 8in in many ways like speed and distance,just have to think you need them I think.
A tip I can pass on,I leave the base connected to the car now and bring the boat on the trolley to the base as it does not move around when I pull the hulk onto it. May help!
I also have a spare wheel and a BIG brace,one of thoes four end types that fit many nuts. Found in the past I was the only person to have the right end at one open I went too. Plus lots of leverage too!