I can’t give you the exact dimensions of the spinnaker for each of these classes, but I can give you some relative information from my experience owning both a Thstle and Flying Scot. The Thistle spinnaker carries 20 sqft more area than the FS spinnaker and is narrower at the foot, but taller (longer luffs). An indirect indication of the narrower foot of the Thistle chute is given by the relative length of the spinnaker poles for each boat. The FS pole is 7-feet long, but the Thistle pole is a full foot shorter (6-feet long).
Hope this helps.
Bill
FS 5193 Flying Fish <><
Thistle 1791 Scarlet Fever (former owner)