Thurmond Moore over on the Openbuilds forum has built a foam cutter that uses a MIG welding tip (http://openbuilds.com/threads/brushless-motor-foam-cutter-and-cutting-sheet-foam.5862/). I just ran to Lowes and purchased a card of 10 Blue Hawk brand 0.035″ tips and I’m going to use it on your QC version of the foam cutter. I think they should be perfect for this application and we can size the hole to simply thread these in just like we did with the inflation needle. FAR, far easier than boring out a carriage bolt!
I’ve also printed the QC receiver and pen holder to check the fit… mine slip together surprising well with no adjustment at all. If I torque on it and twist it around I feel just the slightest bit of slop but I don’t think at this point it’s enough to worry about. I’m gonna get started printing as soon as I finish this post! — David