150 mm spacing Rear Hub motor

[Mainer]

Any ideas? I'm guessing that I'll just use spacers on each side. It is a rim brake Burley Tandem. It would be nice to find a cassette style hub motor, rather than freewheel.

 

[Mongo]

Is your rear axle quick release? It would be a spendy build, but I'd consider a 148 Boost thru-axle Grin hub kit with the cassette integrated torque sensor and Statorade, then add a $15-20 148mm long, 12mm to 10mm thru axle to QR adapter.

You'd also need a new rim, if your current one is not 32-hole.