Scrambler Conversion

Moin, a short preview on my part – come from the far north and actually drive BMW R1100 GS, but also have an XL600LM, which I want to convert to the Scrambler! Now just throw the question into the room, has someone done that before? If yes, with tips and experiences. The conversion should run as TÜV compliant as possible! Therefore first the most obvious questions: Shorten rear frame – possible TÜV entry? What max. tire width can I with the Origin Enduro or Trial profile of course!!! Which smaller rim instead of the 19″ fits in front of the fork? And maximum width?! Or which other rims can I install without problems with the TÜV? Which shorter suspension leg for the rear? Ideas for the tank, exhaust and cracker? So thank you for the start and hopefully also for the many upcoming tips?!!! Gruss Tammo