Ole man,
I hope you have good drill bits HSS will not work. You will need Cobalt or Diamond to drill those arms. If you drill them the right size you can use Yamaha sled rivets to gain weight in the right place especially if you drill them in 2 places. If you take a look at Dalton weights with the 2 holes they will allow you to move the weight around. Mind you on a 360 might not be enough power to utilize the weight differential. Trial and error is the stay of the day with the Comet let us know how you make out.