I need to replace the tires (and tubes) on my J3C-65 (719 lbs w/ 4 quarts of oil) 800 x 4 wheels and am seeking advice on replacement tires. My landings are about 50-50 asphalt and grass. A second question is whether or not I should I convert to the 600 x 6 wheel, as I understand the tires are a lot cheaper - I am in my 80s and it probably depends on how many tires changes I will make. I have the Grove disc brake conversion on the 800 x 4 wheels. A third question is whether to have the existing calipers rotated (listed as the "added alt caliper location" change, i.e. Change letter C to Grove Installation Brake Assembly Drawing No. 76000) to my existing Grove disc brakes as I have already cracked the copper tube line while taxiing from the grass to the asphalt. I guess I am asking if anyone has any bad experience with or making this caliper change. It looks like it may give a couple more inches in clearance. My IA has quoted me at least $500 in labor to make the caliper rotation. Thanks.