Well, I like 13mm shafts.
When I look for a cue, I also respect the cuemaker specs.
I pretty much stopped looking for the holly grail because I have 2 cuemakers on my list that I absolutelly love - Sugartree and SW.
My post is based on that, 13mm shafts.
If you like 13mm shafts and want to try something new, might as well buy an off the shelf blank and have it tapped to the cue cue pin specs. Many times Mika told me I should play with a 12.85mm shafts but I still prefer the 13mm diameter.
you know if mika told me he thought a change like tip diameter could improve my game i think i'd give it a shot. there's always the chance that he's just trying to sell you a shaft but f*ck it. i'd give it a shot