I'm working on it but have yet to break through the dorsal ("upper") side. You can see part of the problem in this pic - there's vertical asymmetry in how deep I've been able to cut, with the groove getting shallower towards the tip of my cock.

The main issue that I'm running into is that at the very tip of what remains, there seems to be some sort of nerve cluster which is proving to be absolute agony when I so much as brush up against it with a scalpel.

I can see from your own profile pics that you seem to have been able to pull off a complete bisection further down than I've managed so far, so I'd be curious to know if you ran into the same issue when cutting, and if you did, how you managed the associated pain. I've tried slathering the relevant area of the cut in 5% xylocaine gel and then wrapping it in plastic wrap for half an hour to ensure that the gel works into the work area, but even then it barely even touches the pain in the area that I'm going to need to cut through in order to manage a bisection.

Any suggestions?