Structs need to be reversed by basically guessing what got changed.
If this was etmain:
And this was etpro:
Then when you tried to use headOrigin on etpro, it would screw up because of the added int. You must either find all of the added things (and pad, meaning throwing in an int or whatever to fix the pos of everything) or just correct the pos of what you use.
After doing this, you have to kill off the etpro anticheat (which shouldnt be too hard)
I think these are some etpro offsets:
cgs_t *cgsPro = (cgs_t *) 0x33a7b880;
cg_t *cgPro = (cg_t*) 0x33767670;
centity_t *cg_entitiesPro = (centity_t*) 0x337d5f10;