What I prefer to do is use regular laminating Aeropoxy and put some colloidal silica in it to make the consistency like Vaseline. I think it's just as strong (though I'm not 100% sure about that), I can tailor the consistency, it's easier to mix than the thick stuff, and I only have one stash of adhesive to keep topped off.

The structural adhesive is very thick. It helps if the environment you are working in is at least room temperature. (in a semi-heated garage in winter it is like molasses). Thickening it with West System silica makes for some very nice fillets when mixed to a peanut butter consistency.

I use it on all my birds. I have used PL Premium Polyurethane on PML kits on the inside fillets with great results, as you're bonding urethane (a.k.a. water-pipe) with it.

On the other hand, I have crashed some fiberglass birds (flat spins/high speed main deploys) and retrieved intact fin cans made with Aeropoxy. structural adhesive on several occasions.

It takes patience. In my cool basement it takes 6 hours to firmly set up and 36 hours to cure. Benefits include that it flows into nice fillets. You can tape them up and strip the tape after 3-4 hours and leave nice fillets. Other benefit is that there's no rush.

It is very hard but retains enough plasticity to be damn near shatterproof. It does not soften in the sun either.

I heartily recommend it. The con is that it takes days to fillet the fin can.

It's not for the inpatient builder.

I have a 4" fin can/booster that survived impact from 8000'+ - built with West Systems. It has flown since multiple times with a new forward airframe and nose.

I've bought the farm with fins that had PL attached. The PL was still attached to the fins after. I did rough the G10 up with 60 grit sandpaper though.

Edward

I may not have roughed them up enough.

I used finer sand paper.

With my wood fins (on some of my rockets) where the root meets
the motor tube. I cut shallow grooves every inch or so, for more
glue to attach to the fin. ( an anchor )

I may try this also on the G10 fins.