I figured someone else would do it erik. The glue used on mine was black rubbery stuff. Might well have been silicone. My cap was still down and I could not get anything thick under it without possibly damaging either the cone or the cap. So I used cyanoacrylate glue. Capillary effect sucks it right in. You just adding until the capillary effect stops. Then you have a full tank so to speak. Cyanoacrylate is more brittle and it might break down in time. I'm working on MS Tool's Model 4 (when I can use my right arm.) Hopefully they will be done by next spring, up and working.
The Model 3's will be retired. I'm hoping the 4's will be the final version. They are 30 inch long cylinders with a decagon cross section. 10 sides perfectly beveled to 72 degrees made of 1.5" cabinet grade plywood (plywood is stiffer than MDF) The diameter is 15". A 15 inch driver will go in each end (balanced force.) That is #8 15" drivers total in 4 enclosures.
I intend on finishing them in a satin black polyester lacquer. With all that driver I should be able to push 105 dB without pushing them past 1/2
X max which is 12 mm for this driver keeping them well within their linear zone. Large drivers are not slow contrary to popular opinion as long as their motors are matched properly. But, they do not have to work near as hard to produce the same volume. This means much lower distortion levels, the primary goal in a high end system. By virtue of the design of these encloses distortion should be lower still.
Anyway, the point of this thread is to let people know this happens and is very easy to fix. If your woofer is belching or burping with aggressive low notes (play some Hip Hop) check the dust cover!!