those bolts are crap ! the bolt goes into shear when you tighten it (as the seat lug closes, there' a bending force put on it) and it's just a pot metal part.
here's what you might do - KEEP the "nut" side of the seat binder bolt. Find an M4 or M5 bolt, stainless steel, allen head in your junk box (you DO have a junk box right?) and use that as the "bolt". MUCH stronger. You may have to come up with a washer or spacer to make it work. On one bike I turned the bolt head down slightly so it would fit in the frame recess.
If the post fits properly you should not have to tighten the bolt that tight. 5 or 600 foot pounds should be sufficient
Seriously if 72 in/lb (6 ft/lb) is not sufficient then you might consider adding so punch marks or knurling the seat post below the insertion line to give some increased "bite". I have the excellent Stein knurling tool and do this on most bikes after I haver the saddle height finalized.
Mark Petry
Bainbridge Island, WA USA
