weight aloft

[Brion Toss]

Hi,
Go sailing in the steadiest breeze you can find. While on the wind, measure your angle of heel, and of rudder, then hoist a weight equal to that of your new fitting to the masthead. Use a carefully-tended downhaul. Recheck that heel angle, recheck that rudder angle. At the weights and distances you are talking about, this will probably have an effect roughly equivalent to having a large person camped on the leeward rail. It will mean reefing that much sooner, spilling that much more coffee, steering that much harder.
You might then want to look up the origin of the term "overkill," and think about whether that is a useful term here. Base your scantlings on load-times-safety-factor.
Fair leads,
Brion Toss