It can't be any worse than the factory trunk seal, which doesn't seal for shit. The biggest offenders are the 96-97 seals, which seem to have an extra "flap", that sometimes folds under.
The "trough" area near the window needs to be clear of leaves, etc to keep water from backing up and seeping in, but even with that clear, they still let in some water in that area.
97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles