the "compartment" door to the Lower left of the Turret ring... what is it for?

If you mean on the right side of the hull where two holes are on the pic (circled below), it is a storage box for BII (Basic Issue Items) like pioneer tools, hand tools, etc.

The one above that on the Angled surface right next to the turret ring... I assume it 's part of the Engine compartment?

That is a blow off panel for the ammo storage in the hull. It only holds 6 rounds and is kind of an emergency backup as I hear.

Nice....... it can disappear on my Build then....LOL

These are indeed (two of four) the hull blow off panels. There is also a set underneath at the bottom of the hull. These plates are sealed with silicone (RTV) and lie in grooves, secured by clamps with two bolts. They are covered with anti-skid. These are also the repair access panels into the hull ammo compartment. I wouldn't recommend "losing them" on your build, (not sure what you mean here) they are a very important feature on the vehicle.

Steve

it's not gonna be a tank.............................. it's a fictional ARV............ for the ACUTR campaign / groupbuild

OUCH!! You're not doing that to the new Dragon kit. I'll trade you any other Abrams kit and some other kit for the new Dragon M1A1 AIM. Let me know.

NOOOOOO it;s the Older Tamiya (w/ Plow) Kit...... bieng salvaged from about 13 years ago (damn that long already????) I just used that Sprue pic cause it was a "quick" find........

O.K, you had me worried.