Idle Problems W/75mm Tb?

I have a 331 w/10.2 pistons, TW heads ported, a GT40 intake and the CompCams xehr274 camshaft. I am still running a 65mm TB and feel like I need to upgrade to a larger one. My problem is that I read that the 75mm gives idling problems and that you have to drill a hole in the butterfly to make it work. The 70mm is only slightly less than .200 larger than the 65mm.
Come on you motor heads...help!

I believe that I saw it written in a MMFF column where the reader writes in with problems. The person may have been trying to put the 75mm on a non-modified engine or something. Maybe it is not an issue.