If you mean to couple two together then im not sure but with the inlines they run fine when using stock zenoas but as soon as the zens are modded the cranks get twisted on them so ive been told.Id say a stock rcmk is similar power wise to a mid mod zen so it could suffer the same im not sure .Mind you the 4 bearings on the rcmk might help stop that,the Qd motors use 4 i believe to overcome that issue so it might be fine.Im sure an engine guru will be along to better inform you
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Mart