I have an automatix freewheel which I plan to put on to my tsdz2 setup. I use it on a daily bike at the moment and Ive done the mod to have the second gear switch over at 15-16mph. I am also torn between just putting a 58t chainring on. It is a regular automatix so the main issue for me is that i lose out on my rear disc brake. There is a disc brake version but it is 135mm and my rear drop out is 120mm. There is also an disc adaptor available also made by a company in germany - cesur.de i think, but I havent looked to much into it.
The tsdz2 tops out at 90ish rpm where the assistance seems to drop, because I cannot generate enough torque for the sensor at that rpm maybe. It doesnt feel like its runnning out of power - if I spin hard to maybe 100rpm, I can still feel the motor kick in to top a little over 23mph. Its just I cannot maintain it that long.
Im sure that an automatix will allow it to go beyond 22mph if rpms are low.
I would run the the same 13t cog on my setup with it because it the tsdz2 can handle the climbs already and at higher speeds maybe mod the automatix to switch over at 20mph if possible. The automatix second gear is 133% I think so 109 gear inches.
Saying all that, I am happy with how my tsdz2 setup as it is...for now.