Frankly, I have no idea why the inner tube is so beefy while the outer tube is kinda thin. I like the kit. Trust me! Just wondering out loud.
Practicality ...... There are both thick and thin wall 38mm tubing. Remember most 38 airframe kits have 29 motor mounts in them
Thin wall airframe opens the door for 24mm motors, because it is lighter.
Thick /standard tubing is used in a variety of kits for both high power, where as thin wall [which is lighter obviously] is more for smaller mid power motor motors that would not fly in the same kit made of standard. But the beauty of thin wall airframe,it's still strong enough to fly the biggest 24/29mm motors that will fly.
Since 38 tubing is used for 3 things I know of...motor mounts, airframes & minimum diameter airframes. The standard is used where it's needed, thin wall, when you can get away with it.
That's the back ground, now moving forward:
There are no 24/29mm kits I know of using thin wall and if there are, it's darn few... so 98% of 24/29mm glass is standard wall & just used for motor mount ,
There is no need to use anything other than standard 24/29 mm motor mount tubing that would increase the price. So it just looks funny staring up the butt of your rocket when the 2 tubes are different diameters, and the smaller one has thicker walls than the larger.
The final straw is :
There is no need I can see of, for both thin and thick wall 24 & 29 since most if it is used just for MM's where as 38 is used a lot for both airframe & motor mount.
If you did have thin wall 24/29 motor mounts, the kit makers & vendors would have to carry 2 different sized Centering rings for the same thing. Since the ID of 29 tube are the same inside but the OD would be different between the standard & thin. So now you need 2 -24mm to 38mm Cr's. The OD the same on both, but the ID different, yet so close they could EASILY be mistaken for each other when parting out [assembling] kits.
Crap like this [carrying triple inventory parts for no good reason] are one of the things that drive kit makers nuts!
So bottom line is. There is no need to make 24/29mm thin wall ,that's why they use standard/ thick.
You get a real nice light weight rocket, that will fly on larger variety of motors, still allowing the biggest one you can stick in the pipe.
Can still handle all this for are really , really nice price point...where as standard wall airframe , would not allow as for this scale of economy. Thin wall airframe matters... the standard wall motor mount doesn't... for all the above reasons, hence the visual anomaly.
Right GT........