If you have a "mass Invite" macro, add
Code:
/console maxfps 20
to your alts and
Code:
/console maxfps 100
This will cap the alts fps and give more fps to your main

My invite macro looks like this
Code:
/script AcceptTrade();
/console maxfps 100
/stopmacro [group]
/invite alt1
/invite alt2
/invite alt3
/invite alt4
Since you have to invite your group anyway just add a few things to it so it does more :P
Hope this helps you in someway!