Will T70H hold a 29mm or 38mm motor? Yes. With its 2.175" inside diameter, it can hold a 54mm motor. That's in the K range. That said, the 0.035" wall thickness is kinda thin for a motor mount tube at this impulse (K) level. Typical 54mm MMTs are around 0.060".
Can a T70H airframe withstand the forces encountered during a typical H motor flight? Yes. The 0.035" wall thickness is the same as LOC's 2.56" body tube which can fly on H's and I's all day long without any glass. And it can take high speed (early/late) deployments fairly well, too.
Although not impervious, you should find the T70H quite rugged without any reinforcement. In fact, this is one of my preferred solutions over glassing BT-70. Why bother with the mess when you can get T70H? [/rhetoric]
That is the feedback I was hoping for I have a spare 38mm mount sitting here waiting for a tube. Just need to sim up a nice rocket with the BMS parts ;o)