Are there any problems with using carbon fibre tail patches on a polyurethane / polyester board? I have noticed that most boards with these patches are eps / epoxy.
Also, what might be a fairly standard glassing schedule? I normally do a single 4oz layer on the bottom and double 4 oz layer on the top.
That is standard on stock board. The last several daily driver shortboards I have ridden have only had 4oz deck 4oz bottom. I don’t know where the guy was getting the boards glasses but they were as solid as a double 4oz deck and a 4 oz bottom. My friend was doing carbon fiber patches on his boards last summer. I don’t know how much of a benefit that it would offer, the weak link in that equation is the resin so for the cost it might not be the best idea.
Carbon takes PE resin just fine. You'll pay an ultra premium price for light weight carbon other than 5.6 oz. if you can even find it. You may be building in a " hard spot" where the board will want to break if its only a partial covering, don't know about that for sure.