You've gotten terrible advice here. The K97 was the right call to match the C133 (and you did good). Jumping down to a K87 from a C133 is too big a jump (from ~72 down to ~58 cm width is too big, an 8 cm gap is better).
From a 65 kg rider experience to somebody my weight, I have no problem to toggle back and forth between a Kombat 86 (59 cm wide) with 6.9 sail/30 cm fin combo and a HS105 (77 cm wide) with 8.2 sail/32 cm fin combo during the last 15 months of practice. I would appreciate to learn why you think a 8 cm wide gap would be better than 18 cm ? I'm also curious to know your weight.