I used to play with a firmer/stiff arm/wrist when using racquets with lower swingweights but have loosened things up going to higher swingweights. I think that watching Federer has made me modify my backhand so that the wrist is looser. This is a hard transition to make because you don't know if your wrist is strong enough to handle it not being completely firm. I think that this style helps a lot of you stand relatively close to the baseline and your opponent hits fairly deep shots to your backhand.
I've been all over the place with swingweights and have tried various Pro setups. Berdych's setup is too much for me. I got used to the 360s but acquired a set of matched frames at 386 and that's what I'm using now. I've made some adjustments at the higher swingweight. The biggest adjustment was on the serve. I can't use as much arm at that swingweight.
I could have just taken some of the lead off those racquets to make them lighter but I like to leave matched sets as I received them.
4 x IG Prestige MP, 70 cm, 376 grams, 386 SW, ALU Power @54, Prince Syn Gut 16 @58