Well, one could argue all that twirling and moving the stick around over great distances is thus useless once you actually have to move something with mass, so we could say you need to change your technique completely, or only use the light rattan stick.
I am not going to go there though as I have been told I don't do the real FMA.
For strength training I purchased a 24 inch length of steel pipe(natural gas/plumbing line) and a length of threaded 3/4 inch steel lag bolt. I coated the lag bolt with 2 part epoxy and shoved it inside the pipe. I capped the ends with more epoxy. Very heavy and the perfect device for checking that your hits are all aligned bio-mechanically. Makes you learn to align the wrist at all times and move the weapon with the trunk not the arm.