Scott with the 912 you'll notice very little if any difference in performance with the Grove gear. I didn't on my model 3 except the ground handling was vastly improved. Added weight is always a concern on any Kitfox but the added safety to every flight exceeds any penalty you pay for the net gain.
The Grove gear for the model 3 & 4 Kitfox weighs 24.3 lbs. Of course you'll subtract the weight of the original gear from the Grove gear to get your net increase.

Another gear you might check out, if you haven't already, is the new gear Kitfox Aircraft has for sale.
More of a bush type gear. Not sure what they weigh but they are on the Kitfox Aircraft website in the parts catalog on page 35 part number 13050.000 for $1450.00.