i have been thinking about adding a little weight to my TL flywheel as well. but not around the outside. could a round plate be attached to the hub of the flywheel around the riveted area? it looks like a 1/4" thick disk could be attached there but i still need to do some measuring.
you can do a lot with 9hp and a heavy flywheel. remember those huge steam powered tractors that first plowed the hard packed midwest plains? 9 hp and a heavy flywheel.
i don't expect to plow my garden with the TL, but you get the idea.