"He who marches out of step hears another drum." ~ Ken Kesey
Wow are those old.. that design went out sometime in the mid 90's. If you paid more than 10 bucks each.. sorry bro .. shrug.. Oh yeah.. don't use them in a dip tank as they will leak.
The tube and locking channel have basically stayed the same over the years with some changes made to improve rigidity. It's the ends caps of the tubes and the corner pieces that have changed. They did paint them blue at one time, but all that did was chip off over time. they still make the M3 tubes in blue while the mzx are natural. Just by looking at a frame is hard to tell it's age, you have to take it apart and look at the end cap. The first design had nylon end caps and those were a train wreck. had to start somewhere. With this style you have, the tube end cap is made from an aluminum alloy casting with a recess to trap the nut from spinning inside the tube. This end cap had the nut glued in place, then using epoxy the end cap was basically glued in place by hand. They stopped using that for the problem you have now along with the epoxy would give way and you could remove the end cap. Like was said, you can use a pencil to re-trap the nut and then make sure to use some Copper Anti-Seize compound on the end of your bolt. If you don't, you ran the chance of corrosion buildup from reclaim, and trying to loosen the nut, would fracture the back of the plug and the bolt and nut would just spin.. dead tube I called it and I had many back in the day. After the nut problem, they machined the end caps to be internally threaded with a longer bolt. Solved a ton of problems however it made a new one. When a stainless steel bolt is threaded into an aluminum alloy and placed under torque, 55 f lb, and then placed in a salt solution (reclaim powder is a sodium product) oxidation caused corrosion and a metallurgical bond of sorts seized them together.. more broken end caps. The addition of copper based anti seize, new cast and machined corners to accept a shaped plastic washer disc to seal out the water solved this, but required a check up every so often and the discs would crush and leak water into the tubes. around this time is when dip tanks were becoming all the rage and suddenly, all those old frames that had 'mechanical' problems, brought to the forefront the leaking issues. There was also the problem of bowing under tension. There was always some bowing in the long tubes, the M3s had stiffening rods in them and people would buy the cheaper MZX frames to use on their autos, tension them to 40n and warp the snot out of them. The fix to that is what we have now. A solid cast and machine threaded end cap with a black bolt with anti seize baked on. The corner was re-shaped with a 3 degree angle so when you lock the bolts, the tube was forced outward to aid in the bowing all pressed into the tube. no more leaks, no more seized bolts and the bowing is minimal. be it 25 years old or bought brand new last week, you still have a better product than a static frame. Get those nuts in place, use some good lube, put a polypropelene washer behind the bolt with a washer and torque to 35 ft lb. be cautious for leaks in the dip. hit up Shur Loc for some mesh panels
John is the expert but I know of many ppl that use them for the exact same reasons you state, shouldn't be an issue.