Changing that defined var MAX_PARTY (value of 7) just on the HTLauncher wont have any effect if you dont change it too on Server.
By the way if you change that, you will mess up other things that use that var, for example the 3 dimensional array g_pFormation unless of course you know which values you have to add to it (char g_pFormation[MAX_FORMATION][MAX_PARTY][2]) as you may see it is a 3 dimensional array which use: MAX_FORMATION =5 for max rows, MAX_PARTY=7 for max columns and 2 for max height. I dont know for what is used that 3d array.
On both sides that array is declared with 50 elements of 70 that can be stored (5*7*2=70), some of them are:
char g_pFormation[MAX_FORMATION][MAX_PARTY][2]=
{ 1, 1, -1, 1, 1,-1, -1,-1, 1,0,
I think (because you define yourself as developer) that you know the rest of the values stored on that array and most probably that you know for what it is used for and what is stored on the left 20 elements after was declare.