Correct. The the mount itself is in the coupler. Coupler slides into the BT70 which was installed inside the model. Two motor hooks which I also fabricated from wiper blades hold the coupler in. The new Estes style hooks would work great here. Old style will work, but might make it a little tougher to get a hold of while trying to slide the coupler in and out. The TR115's on the forward end of the mounts slide over the blue stuffer tube coupling(which you can see inside) and seal up the works once it slides in. The notches in the top of the BT70 coupler allow it to slide past the top of the BT70 motor hooks. Otherwise, it would stop right there at hook and wouldn't slide in all the way and the TR115 wouldn't get a chance to seat/seal with the stuffer tube. I'm guessing it's pretty important to make sure ALL the centering rings are perfectly centered. Otherwise, you may have problem with things seating up properly. I must have done something right, because mine couples ok. It takes a little finesse to get the hook slots lined up and a very light wiggle to get get in to slide in all the way. The important thing is not to force it in.

I didn't use any epoxy on the motor hook slots, but I may have put a dot or two of CA there...I can't remember now. You do bring up an interesting point though. I can see where some of those high heat areas at the top of the mounts could use the added strength and take the heat better, but really no more than someone building this without the mod. Did you have problems on any of your models in those places which caused you to consider using epoxy? ? The good thing is, since the mounts slide out, if any of those part wears out or needs to be repaired it can be done very easily. Another good thing is, when prepping the motors for flight, you can do it away from the model and then slide it in when your done, possibly reducing the risk of damaging the model during prep.

One area your comment has caused me to look at is that blue coupling inside the core tube. I can see that getting crusty and brittle after time, which may not hold up to the stresses of sliding the mount in and out. I may smear a little epoxy inside that thing now that you mention it...that should help reinforce it and protect it from the heat.

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