Two links to óld articles in Dutch. Worth to google trick an read.
http://www.moturist.nl/kawa1300_1.html
http://www.moturist.nl/kawa1300_2.html
Very much applicable to mý dethrottled R18 with Velorex.
Way longer wheelbase, better front rubber so less ´snow plow´ and because the Velorex lighter and MUCH more slippery to air, the dynamics are both less and more extreme.
I pushed the limit and under favorable (did not appear that to mé

) conditions got to the limiter. NOT to be repeated.
Above 150 you notice the margins of error getting narrower. Above 160 it gets increasingly irresponsible. No because it it unsafe persé but because there is NO room for error or correcting unforeseen.
Anyway tested it nigh half a century later and nothing has changed which stands to reason because the concept of motorcycle with sidecar is the same.
To add a factual perspective:
The Z1300 had 115 N⋅m (85 ft⋅lb) @ 6,000 rpm.
Our R18 has 158 N⋅m (117 ft.lb) @ 3,000 rpm.
One thing which draws my attention is Guus vd Beek observing that with the Z1300 Moturist the limitations of the concept of a traditional motorcycle and bolted on sidecar are crossed.
The R18 has 40% móre torque (mine even more) and the Velorex is lighter than the Moturist.