Bummer, about the fully cracked surrounds.
FYI, I'm not aware of anyone in any of the forums ( that I frequent ) who's replaced an Altec or JBL linen or paper surround ( although maybe I'm just not paying close enough attention ).
Therefore I'd also say that you're in unchartered territory here.
The
other surround source ( mentioned over at AudioKarma ) looks to be the better choice for surrounds.
Some advice; keep all the hardened goop that you collect ( including the stuff still on the old surrounds ).
- You may need to reconstitute it ( if possible ) so that you have a backup supply of something original.
The stuff mentioned in this other link might turn out to be a formula that leaves the new surrounds too stiff ( with a higher than desired Fs > that would need to be measured by doing an impedance test ).
Also, it might be a lot more straightforward to simply make new baffle boards with the correct woofer cutouts ( than to shave back the existing holes > though I don't really know if there's a nifty router bit made for just that job > hopefully ).