Hi Hono,
I'm thinking about replacing the front suspension same as you, except mine come from a WR450F. I spoke to the suspension specialist and told me we should pay close attention on fitting the brakes, mainly. Apparently the only issue is to switch to the proper spring rating which, as you'd mention, has to take into account the extra weight.
But first, we are going to try new springs and race tech emulators to see how it feels. I do mostly off road riding and the roads here are Baja 1000 grade! So I need to shave some extra weight of my bike by installing a 2 in 1 exhaust system from metal mule. At any rate this is just the start and hopefully, with in a few months, we'd have built a new dessert queen!
Cheers from sunny Sonora Mexico.