Hi Andries, great to hear your trip back is still on track.
The fasteners you are refering to dont have specific tourque settings, like documented. The general rule when tightening a fastener which passes through an auminium pipe, or for that matter any hollow struture, is just enough without distorting/squashing the pipe/structure. Generally the nuts on the trike are nylock or castle nuts, so they won't come lose. The following is recommended by engineering companies where torque settings are not specified individually:
Bolt/Nut Size----NM
4 mm 4
5 mm 6
6 mm 10
8 mm 24
10 mm 35
When asked, Hans will tell you to tighten the nut just enough.
