The line terminus should have some bugscreen across it to keep insects out irrespective of wool (but definitely required for wool). You don't want things laying eggs in there or moths eating it. Personally, I'd get a bag of polyester pillow stuffing (aka polyfill)...or a pillow from Walmart. Maybe two. Upholstery batting works great, too. There are other similar (aquarium) or quilt-batting products, too (see attachments). Fiberglass is a pretty big hammer--more resistive than what a line needs (but it Will hammer the lowest harmonic in your line if you stick a full cross-section halfway down a straight line--tapering lines changes that).
Tease (not kidding) the polyfill apart (it is dense as shipped if just sold as filling). It's even pretty dense as shipped in a pillow. It will take some experimentation if you can't characterize the drivers.
Labyrinths were usually just lined (unlike TL's) but I'd fill the thing, too. The only questions are the density and the quantity (ie it doesn't have to be distributed uniformly everywhere in the line--in fact you might want only the top 60% or so filled...or not.
Get the length of a string that would wind it's way (shortest dist) from the speaker to the terminus. Make a straight cardboard tube of that length and bung-together a cardboard (or masonite) baffle to use to test with the real speaker. This way, you can run it live and screw with filling that you can reach-in with your arm and figure out where it sounds best. Acoustical resistance of materials is frequency-dependent. Try stuff (tm).
I hate how masonite sounds, but it'd be better than cardboard UNLESS the cardboard is truly packed pretty tight with dense polyfill. That used to be how we proto'd little single driver TL's (with packing tape and cardboard) with new drivers in the late 80's
That can sound really good in a short line--better than you'd think.
The deep cardboard baffle voodoo I figured-out was to line the rim of the hole with packing tape, too, so it had a good sealing surface. Then put a ring of mortite around that and set the driver frame on the mortite. What's more, sheet metal screws can sort of "hold" with the packing tape (vs. raw/bare cardboard). The rest of the cardboard "line" (folded square/manual/tapered whatever) is also sealed with packing tape. In this way, one can utility-knife-up and tape-up various configs very fast and the results are far more reliable than one would think (and vastly better than one blind shot and hope/faith).
All that said, the Strombergs I knew about had one LF driver and one HF driver so not sure which one you want to play what. If you do experiment with a straight tube and if you are trying for low freqs, it's worth trying one with stiff walls--that loss comes right off the bottom of the bottom of freq response of the lines.
The other thing is that the partitions shouldn't leak, if you can find a way to do that. I'd just lay a bead of whatever if you can get at it. I know you're not as intense about this as this post sounds, but it's worth it--it defeats the purpose if the runs leak.
If you want to positively enchant the bar denizens, you could swap-in some contemporary widerangers that don't need care and feeding of field coils. There are many small Markaudio drivers that are quite good and a couple that aren't expensive, as one example (if the impedance can be worked-out).
Fun project--please drop some updates if you feel like it. Think of it as an excuse to listen to music and mess with filling. Your ears will notice things. If you can, balance heavy percussion (likes a lot) vs big soundbodies (don't like much) and somewhere that voices don't sound like they're coming out of a tunnel
