I took my full built EBMX build out to see what the true kilowatts I was able to get. Kilowatts is battery amps x battery volts so, so the max I could really get is 28kw, even tho the app says 30kw.
I'm not 100% sure, but the EXT fit the standard surron the you shouldn't have a problem with the EBMX swingarm as I still use the stock rear shock in there