Happy Holidays!
I use a 35.0 Salsa Lip-Lock and no slippage whatsoever.
For starters.. When ordering this frame, you're given the option of purchasing the headset with the frame which at first seems ideal.. There's the standard Neko headset that costs about $15, and some vendors give the option to upgrade to a FSA headset that goes for about $25. Form my research, I recommend passing on both options and buying the Cane Creek 40 series headset that can be found here: http://www.universalcycles.com/shopping/product_details.php?id=39924 and here: http://www.universalcycles.com/shopping/product_details.php?id=39947In case those link destinations change.. That's the "Cane Creek 40-Series IS42 Integrated Upper" and the "Cane Creek 40 IS52 1.5" Integrated Lower As"It seems that some guys are running into some issues with both the Neko and FSA headsets, in that special shims may be required to make the headset fit properly. Now perhaps this problem only affects a small portion of users.. really not sure.. but either way - both of the cheaper headset options seem to wear out prematurely. Of course, make your own decision, but personally, I read too many negative things about the headsets to want to put it on my super pimp carbon frame.. The Cane Creek for me 100%.
It looks like the IS52/30 is for a straight steerer and I have a tapered steerer so the IS52/40 it is then.