Good question. Just need a little more info to be able to answer it.
What weight is the rocket? What diameter and length is the BT?
Once you get over 4" diameter, you can use a quick link to attach the shock cord to the eyebolt. If the BT is smaller then that, you'll need a thin hand to get in there and get the link attached.
I have a 4" dia. rocket and tied the shock cord to the quick link and attach that to the eyebolt.
I also have a 2" ID rocket with a 38mm MMT. Besides not being able to reach inside to attach a shock cord, there was no room for an eyebolt either. I used a steel cable with a loop in one end that extended almost to the top of the BT. I bought a couple of feet of 1/16" steel cable and the crimp type connectors for it. They crimped a loop in the end of the cable when they cut it for me. The two crimps were more expensive then the 2 feet of cable, and the whole thing was still less then $2. I used JB Weld to attach the cable to the MMT.