I use a 45mm. I think I tilt the 60mm one and it cuts mine a little skinny. Also, I have changed the length of the strip I am cutting. I no longer cut a single fold WOF because I don't have a long reach. I use strip rulers and they are AMAZING. I take half WOF and fold in half again to make the cuts and to fit under the ruler. This takes longer. I also have arthritic hands and the strip rulers help a lot for accurate cutting AND saves my hands. I put a weight on the corners just to help hold it down. I suspect sooner or later I'll need an Accucut cutter or something similar.
I have also heard the type of surface under the cutting mat makes a difference. So you may want to try a different table and, of course, a different height. Try different techniques and you'll find the one that works for you.
Let us know how it goes.