NoNoise, I appreciate the compliment but I don't think you should hold back on posting your LiI conversion. Function is always first and if it gets the job done as you intended then it is a success!
I don't have the chair but I have another project in the works for him and I will get your fully charged voltage measurements the next time I can get my hands on it.
Attached wires might be easier to work with if they are directly welded to the cell ends but I haven't seen any done this way either.
It sounds like you have your chair set up very well for your use. This chair was one of the early units (Cannondale AL frame) and the frame was not sized for him (too short). The chair spends a lot of time on the wheelie bars due to this. This was sort of a test to see if he will try to transfer the drive tech onto another chair or order a new chair that is properly fitted.