I put a Kenny Brown strut tower brace in mine four years ago, and I have no issues with it. It came with cheap hardware, but I bought some grade 8 equivalent stainless 12 point bolts and nyloc nuts from ARP to mount it with. I felt like it firmed up the front end a little, but that's probably because I shelled out $120... The coil packs had to be maneuvered around, too. 6 holes to drill, no big deal. Measure and mark twice, drill once.
JL wasn't making his parts yet when I bought mine, but everything I've ever read here about his stuff is positive, and I'd venture to say he'll back anything he makes up. Rich has been around a while, too. One of these days I'll get around to the other braces.
My Fiero GT flexes big time, since I put the polyurethane bushings and lowering springs in it. I can see cracks in the paint all around the sun roof opening. Someday I'll figure out how to stiffen its chassis structure up as well. I'm a firm believer in the theory that the suspension needs to do the work, not the chassis. The less equivalent unsprung weight, the better.
97 LX, 4.6, Dynomax catback, Mustang MAF/intake tube and Aviator throttle body, Xcalibrator2 by Lonnie at BOC, 180 t-stat, Super Coupe wheels with 235/60/16's, Kenny Brown strut tower brace, Tokico Blues, Eibach Pro-kit, some strategically placed MN12 Performance polyurethane pieces, '02 Grand Marquis transmission
Submariners do it deeper...