Possible: Directly going from i55 to i75 tool

[AttacKat]

It says 120~140 pairs at a rate approaching 20%, with the remainder (approximately 75-80% of the total) coming from weapon parts and clocks at a rate of about 1/3 after recursive desynthesis. The price tag for that is going to vary depending on your server and the day, but it's going to be an eight-figure number.

Then right below:
96 Rose Gold Clasps
50 Rose Gold Ingots
15 Fieldcraft III
4 Clear Demimateria III
27 Darksteel Nuggets (40 total, 14 single and 13 double)

That is a VERY expensive experiment w each costing on avg 40-50K just on peacock ore. Cost, is the main reason why most ppl went the CUL route.

Edit:

Before I waste a bunch of time doing this what is the drop rate on the Artisan Spectacles desynth for the master craft materia?

GSM Dsyn <70%, 21 specs, 2 MC, 0 FC3
GSM Dsyn 70<76%, 34 specs, 4 MC, 4 FC3
GSM Dsyn >=76%, 17 specs, 0 MC, 4 FC3

Haven't cont to do more to raise GSM Desyn lvl.