BE VERY CAREFUL

your batteries are the most expensive part of the conversion kit.....

I have seen racks that are designed to be bolted onto the 2 suspension bike, and just by looking, i would go with that........ it bolts onto the seat, so the batteries would be suspended as well.....

considering the cost you have already gone to for the kit and batteries, i would hang off and wait until you could afford the proper rack for your bike....

riding ebikes is fun but
are bad

hope this helps, let us know what you do and how it goes