my strategy (with Bryant's 2.6g mod, but it would be the same in the original demo, probably), is to have a ton of T-4Bs, and land 3 T-4Bs and 1 T-2B.
I send the units on the right to capture the reinforcement point, and the upper on the left to capture that point, then the lower left to capture the mercenary bunker. As soon as I have it, I research Survival Training (my missiles now own! w00t)!
next, I bring down seven or eight T-4Bs (total) and two or three T-2Bs (total). I've found that they can own anything. Plus the T-4s can fire through the shield (with their rockets), while the T-2s own any stormies.
Then, I send them in in a frontal assault, firing rockets until through the shield, and then firing lasers with abrupt bursts of rocket fire before returning immediately to laser fire (this gets a salvo of rockets off, while not cutting down too much damage give-out from the lasers, as I believe the lasers are the more powerful of the two, or at least the fastest firing).
With this strategy, every single time, the Empire falls. I usually just forget bout the jawas/indig humans because I really don't need 'em.
and even if the Empire sends storimes to take the reinforcement poitns, I just send a couple T-2s out there, then, once the stormies are cleared, send the indigs back in.
it's really a very simple map.