I would go with something stronger than the elastic; there are a couple of reasons:
(and take all of this with the grains of salt that I've really been into this hobby for less than a year, but these are what popped out at me)
1. In addition to the G-forces at ejection, a 6-foot 1kg rocket is a pretty big thing. As it descends, the wind can and will tug on the body, making it pull/twist/spin.
2. When those forces disappear, the elastic is going to tend to want to snap back with a lot of energy. So your NC blasts out with a 30g ejection force, the elastic expands, and maybe 80 or 90% of that force is dissipated, but even if that NC/upper section comes back with 2g of force, that means that a 1 oz NC is going to smack the rocket like a 2 oz blunt object. At the very least, I'd use Kevlar inside most of the body tube - that cloth can get burnt with repeated ejection charges, and then you're stuck replacing the shock cord (which is no fun). Kevlar is fireproof and relatively cheap.
https://www.wildmanrocketry.com/ProductDetail.aspx?product=2922 would be the good sort of overkill
A double-length of this would probably be plenty:
https://www.amazon.com/dp/B00ABV7FW4/?tag=skimlinks_replacement-20
3. I'm not a fan of the fold-over-paper shock cord mounts on smaller rockets because they can reduce the available area for a chute. If you really want to do a tri-fold mount, what I would do is glue the first section with JB-Weld, let it cure, fold it, glue it with JB-weld, let it cure, then use a heaping gob of JB-Weld to attach it to the inside of your body tube. JB Weld is good because it's relatively resistant to high temperatures. (I'm wondering why you're avoiding motor mount solutions ... is it already glued in? If so, okay, we can work with that!
I think that, given the rocket's length, some sort of surface-mount shock cord should be OK. The key will be to spread the load out over as much as possible of the body tube. (presuming the BT is cardboard, and on a 6 foot 2lb rocket....I'm thinking it's cardboard.) Open to suggestions from others on here, but you might try something like this: Make a "U" out of heavy kevlar cord (like the Wildman stuff I mentioned earlier) and use a healthy gob of epoxy to attach each end to the inside of the rocket tube, below where the chute will go (so if the rocket is pointing up, the U is upside-down). That should give you a solid anchor.
Oh, one more thing. If you ARE using cardboard, I'm going to go back and change my mind about a previous thing: You do want at least some of your cord to be elastic; kevlar will zipper that body tube like a knife through butter. What might work is something like this:
Kevlar anchor -> Kevlar cord to JUST below the top of the body tube -> two-foot-long loop of elastic ->Kevlar to the nose cone
Then tie a loop in the middle of the elastic and attach your parachute to that.
Good luck!