Max level to group with list?

[syztem]

I could've sworn there was an old thread laying around with all the levels done each with what they could get exp with max per level. Wondering if anyone knows the 30-39 range max level person in group before exp would be lost. iirc you need something like 38.5 to exp with a 55, however since there is no such thing as 38.5 it basically rounds off to 39. Is it safe to assume its 39 for 55-59? or is it like 55-57-58? Searched around for the old thread to no luck, terrible with math.

Basically wondering if i should de level to exp with friends, or wait til they get in range since exp at their range is much easier.