Classic JBLs with Aquaplas surrounds...

This probably belongs on a vintage hobbyist site on on the tech forum, but I figure that many of you, as I, have a pair or two of early '70's JBLs around. I have a quartet of S109 Aquarius IVs, which use the special LE-8T2 full-range driver. The only important part of this is that these drivers do not use foam or butyl rubber for their surrounds, they use a material known as "Aquaplas," wich is buff-white and generally becomes more rigid over the decades as it dries out. This ultimately can destroy the cone as it increasingly limits their travel. I disassembled one pair and found one crack in each surround of otherwise mint drivers, so sent these off to an experienced specialist for modern foam surrounds. They decided that the Aquaplas was too difficult to remove from the cones, so did a total recone at a big discount as they had not originally thought it was necessary.

Drivers are now well rebuilt, but totally non-original. The second set of drivers have pliant and uncracked original surrounds (this pair probably experienced better climate control prior to my buying them). I keep thinking that I should have maintenance done on these as well, as they are approaching 40 years in age and I intend to keep them indefinitely-- I run them in quad with the other pair and I'd like to keep their performance parameters the same-- I've also had the vintage equipment driving them rebuilt.

I want to double-check before I permanently alter my pristine pair: Do any of you own JBLs with this type of surround, does Aquaplas ALWAYS deteriorate in a living-room environment, and has anybody removed Aquaplas without damaging their cones? Were these guys experienced, but just lazy?