If you go with Sorex, I suggest 32R min. Some electric racers might want to run 26R (the lowest I've found!) for max grip but I don't think it'll last for very long even with hard inserts. Go with 32/36R and maybe you can try the soft/med inserts. 40R for max tire life. Your V-One-S is heavy, so it'll eat rubber very quickly.
On a hot afternoon, I think track temps can go to maybe high 30s C althought I don't know for sure (never thought of taking temps!). Next time we have an F1 race in Sepang, see what the commentators say. It won't be the same since F1 tires run very hot and lay down rubber on the tracks, but you'd get the idea.
You know why there is a racing line in a race? Its because the drivers want to take advantage of the hotter temp. and extra rubber laid down by all the passing cars.
Hot=more traction, but extra tire wear.
Cold=less traction, longer tire life
That's why, an F1 driver who wants to keep his tires fresh tends to stay off the racing line and try to find colder sections of the track....but they don't do this for long coz the trade off is they might lose tire pressure hence losing traction.