A few points about the J-P`strakes and things...
Mk 3/4 had 3 fuel tanks in each wing (appx1450lbs) and 2 tips( 700lbs); Mk5/5a/Strikey had 4 tanks in each and 2 tips ,2900lbs total. The Strikey could also carry 75/100 gal u/wing tanks.
Spinning limits for 3/4 were- no fuel in tips, balanced fuel in mains<100 lbs between wings , and 1300 lbs max.Up to 8 turns permitted.
Mk5 limits are max fuel 1780lbs <100 between wings and pre mod 1791(wing-tip tank mod.ie fitted) no fuel in the tips.8 turns permitted.
If tips were fitted(post 1791), fuel state was ..no fuel in tips, <100 between wings, and max fuel state 1300lbs. 4 turns permitted.
The Strikey was I think a max fuel of 1600 lbs<100, none in tips, and no underwing stores carried-- store carriers could be fitted.
Strakes were fitted to stabilise the oscillatory characteristics by reducing lift generated by the larger egg-shaped front(Coanda) as was the `concrete ` LE of the wing. The 5/5as also had strakes under and behind the intakes, probably for the same reason, or prevent x-flow in spins.
Memory must play tricks Jag, as Strikeys never had any strakes, as the guns were in the lower part of the intakes, and the ejector chutes probably were as effective(unless of course you can show it different !)
The Mk3/4 were quite smooth spinning, recover well 1/4-1/2 turn, Mk5/a similar but can be oscillatory, and slightly faster to the right , recovery 1/2-3/4 turn. Strikey- slower than others4-5 secs, stable, but flatter, recvers about 1/2 turn.
These are of course done `academically` for airtest purposes, not your QFI FLICKING IT IN THE MIDDLE OF AN UPWARD `WHAT-WAS THAT`...
Edited . Also the Cof G position, ,range, and limits were changed and have a considerable influence on spin characteristics, particularly between Mk5 and Strikey.