I have always used the cold + 10% on my bikes and have never had an issue.
Start with the recommended pressure in a cold tire. Load the bike with the weight you normally ride with, then ride until the tires are warm at the speed and type of roads you typically ride. Then check the pressure: it should not be more than the cold temp + 10%. e.g. start at 20 then when warm should be around 22, if 28 then 30.8. If it is too high, then lower the starting pressure a bit and check again. If it too low, increase the starting pressure. It takes a while, but when you are done, it will serve you and the tires well.
Interestingly enough, after you get this done, it seems to vary very little from hot days to cold days. The tires warm up due to friction, and the cold +10% still works! I have had to do some minor adjustments for both weather extremes, but most of the time I just check the cold pressure and go. (If you have the FOBO system, doing the check at both ends is a piece of cake!)