I wouldn't call an 8x5 small, but thats pretty common on H18s. if you fixed it correctly then it should hold up for a few more years. both of our 18s have the soft spots just fore of the rear bar between the grip stripes, aft of the dagger-board trunk. If you don't have them you'll get them one was repaired properly the first time and has been sailing for 8 yrs no problem, the other was done by a 16 yr old with 2part epoxy and as a result thereof it's been repaired 4 more times.
if the problem worsens (and at some point it will) you might have to take it to a boat shop and have it seriously overhauled, but It's fiberglass not crystal, you can fix it no matter what!