Hey Sire -
OK, so.. a) I assume you've realized / checked w/ Delta on your-particular 'fare-rules'.. Most International flights to 'Centro 'merica' allow 70#s as the limit (as-opposed to 50# for domestic...) and I fly Delta almost exclusively, and find that they are usually good for 'up to 5#s over'.. *depending on* the person you get (unfortunately..) Some counter-peeps will be cool; Some are the '1#-over: Fee-applies, sir'-Nazis that are merciless, regardless, but.. I find they are often a bit more 'tolerant' on Int. flights, than Domestic.. Regardless, best to 'strip it of all non-essential' parts - ie: the 'Yoke' can be 4-5#, alone, on some models, IEC can also go in w/ yer clothes, etc, etc..
b) What's the 'flight case'? Have you actually weighed it, w/PJ-inside? If it's one of the 'Chi-cubes' on wheels, I'd recommend a Pelican 1620: http://www.pelican.com/cases_detail.php?Case=1620 I am more than happy to loan ya one of ours (and I could probably 'dash' it LAX > EWR cheaper than ground.. and that's only about 24# w/ the full-load of Foam, so.. You might be able to get it to around 71-72# (especially if you can 'kill the yoke', etc..) And, the Pelican will be much-easier on the 'puddle-jumpers' to accomodate, than one of those 'cubes'..
I'd also call 'Air Sosa' and ask what thier per-passenger limits, are.. You can't be the *only* gringo they've ever transpo'd w/ a 72# bag..
fwiw.. Lemme know if you wanna 'borrow' a 1620.. I would not need it back, right away, either, no worries.. I can just get it when I come for the Install..
j