I am looking for blanks to construct collapsible spinning rods. The rods should be about 6'8'' fully extended; be medium/heavy action; one piece construction where the butt of the guide section collapses into the handle shortening the rod by about a foot to meet airline carry-on requirements. Any suggestions on where to buy or how to construct are welcome. These rods are to be used for freshwater bass fishing in Mexico. They need to hold up to dense cover, heavy fishing and big fish.

From your discription it sounds like your looking for a telesoping blank. Not aware of one that short that telescopes, there were some bass jigging blanks built a few years ago 6 ft 10 in. I remember, think I still have a few All Star versions in the attic.. Your best bet would be a 2 or 3 piece piece blank. Rainshadow makes some that will do the trick. St Croix has 2 piece freshwater and 3 piece inshore travel blanks that would work. Lamiglas has travel blanks also.
MH action doesn't help much as one's MH is anothers H, or medium depending on the catagory, look at the lure and line weight suggestions to pick..

RICHARD,
TAKE A LOOK AT THE BATSON SB843-3 MH OR THE SB845-3 XH.
BOTH WOULD DO A GOOD JOB FOR YOU.
I USE THE SB843-3 I TAKE ON THE PLANE TO FLORIDA EVERY WINTER.
IF YOU NEED A PRICE ON THEM JUST E-MAIL,MIDWEST ROD AND REEL WOULD BE GLAD TO HELP YOU OUT.

Bill@midwestrodandreel.com
www.midwestrodandreel.com

The only blank I can think of is the ATC II MB 703-X 1/4 - 1oz lures. It's a 7 foot rod but I don't know what it's collapsed length is, I have a Shikari MB 762-X which is 7'6" extended and 6 feet 1/2 inch collapsed, I don't know if ATC changed anything about these blanks after they bought Shikari out or not. St. Croix use to make a 6'10" tel. blank but I don't see it listed on their web site any longer.