Ok, I checked again closely. The lower contours on my '89 (which has the same finish as your '87... drool) are somewhere between the ones of your '90 and '91. While the one of my '93 seems to be exactly like the one on your '90.
Also, when looking down from the headstock, the lower horn on my 89 seems to be the 'roundest', while the js has a pretty tri-angular horn, and the '93 is somewhere inbetween. I'll check again tomorrow in daylight.
Seems like it's indeed hit-and-miss due to the final hand sanding stages, as frank pointed out. Damn, this just wants me to go out and buy all of them to get the full experience, lol.
BTW, my JS is one of the '92-'93 HSH models, so it could again be different to 'normal' models.
But, feeling is similar on all of them (not considering different necks and
string gauges here).. But, yeah, none of them is as 'extreme' as your '91.
Edit: Hey ashbass, do you have bigger pictures of those guitars floating around?? Those pics are like.. porn, lol.