My 1715 has a FEL and a frame mounted BH.... I've abused this tractor from ignorance and intention far more than any machine should ever be subjected to, in violation of all the commandments of the god's of machinery. I've sheared the main boom cylinder pin at the BH swivel twice, made my own pin, the next time it pull the entire pin boss out of the BH swivel mount. TIG'd that up, still working. I routinely lift with the FEL till bypass, I've gone downhill with giant rocks in the FEL and had the whole tractor weight (and rock) on one front wheel (twice.....yes heavy enough to lift the whole BH unit too).
Suffice it to say I think this machine is incredibly tough. But...what I was thinking...since the BH frame goes nearly the entire length of the tractor and ties in with the FEL frame via the engine mountings...this serves as kind of a complete "extra" frame under the tractor. Is that possibly a reason I've never encountered any problems? I'm almost over confident in this oldish machine (1993)...seems like you could pick the whole thing up by any part like a kitten and do no harm.
JohnnyB