The T7 with an 18" barrel is still technically .25" short of OAL by my calculation. You'll still need a longer buttpad or something, which is not a big deal if it's using the X95 or Tavor buttpads... it looks like the factory version uses the flat buttpad.29" length requirement, yes. IWI has this figured out and will release a 18" barrel version for T7.
It's cool that DT has released the MDR, but I'd wait for a 20" barrel version, and maybe gen 2. This is their first semi-auto to my knowledge, and that makes me nervous.