Hello,
Full rules for Land Air Mechs will appear in Interstellar Operations. As such we won't be answering LAM rules in heavy detail until then. We will provide general answers, that will help players play these units in friendly play.
The answer to your question is that LAMs can mount external stores only if they have tonnage devoted to their internal bomb bays. These stores operate like a normal ASF in fighter mode and use the TacOps rules for VTOL External stores. In Mech mode, only TAG and Rocket Launcher external stores can be used, treated like Torso mounted weapons.
Thank you,
Joel BC
Catalyst