Thunderhead and Muzzy's are the ones I've seen stay together great and have wonderful penetration. Your bow has enough poundage and should of not done that. That sounds either bad angles or something seriously mechanically wrong. Have you tested the draw weight on your bow and seen it was actually pulling 62lbs? A 40lb recurve will do better than 8 inches of penetration with the right arrow setup. I personally shoot 125gr thunderheads on the end of a 2317 arrow and I've yet to not have a pass through. Sounds wrong a 62lb bow won't do better than that.