The sidecar mounts will need much thought.
Sidecar attachments all at one level will crack how ever heavily made. For ultimate strength 2 high level tubes between car and bike and 2 low level will work. Angle braces then triangulate the structure. You might need only a single horizontal high level tube. This effectively copies sports car suspension except it won't move. Strong and light with minimal bending moments.
It allows forces to go where the bike is strong enough to cope and the necessary geometry is adjustment so the rig can be made driveable.
Have you considered a parallelogram linkage that allows the sidecar to lean with the bike.? This solves all the heavy structural issues as there will be no side forces.
Also what about a mono wheel trailer (leans with the bike) to carry additional fuel and equipment.
i have probably spent best part of two years looking at different bikes before deciding on the 1100,specifically with the mounting points in mind,i have looked at fanums build in great detail .

it would have been a lot easier to have chosen a bike with a proper frame,but nothing else ticked all of MY boxes.
unfortunately the 1100 has only 4 areas where the mounts can be attached,these are all part of the engine/gearbox castings.the load from the side car will have to be spread over all of them without any flex,if the subframe flexes it WILL break either the lower crankcase or the gearbox casing.
if this happens once the trip is underway it will be game over!
two years and a lot of money building the bike will be wasted,in addition to this all of the organisation and planning will be for nothing,also the opportunity to take this length of time out of work will be lost.
with all this in mind, yes the subframe will be heavy.


it has to keep 250kg of bike and at least 200kg of sidecar and payload bolted together over unmade roads,in russia,mongolia ,turkey etc..
mike