>>48240234This isn't a simple question to answer.
The best I can give you is a place to start since every model is different.
First try your futa model merged at only 25% weighted sum. (you can try this with add diff as well If that doesn't work you will have to fall down the rabbit hole of MBW merging.
Get Supermerger, it's the most comprehensive and has the best tools for testing this stuff. I would recommend keeping it on the default add sum option.
This guide and all of it's related links in that section will be your best friend.
https://rentry.org/RentrySD/#111121-block-merging-guidesPic related is an approximation of what block controls what. NOTE: I said APPROXIMATION, do not treat this as gospel, every model is different due to latent variations and other perturbations.
Alpha has the largest effect on the clip encoder, so 0 will keep the clip encoder of model a, while 1 is the clip encoder from model b. Usually, unless you are really desperate, this should just be kept at zero.