The armor HAM cost does not decrease when you gain levels. The player who gave you that info was probably refurring to the HAM cost of specials, which may go down as you gain combat exp levels. (though i can't confirm that)
I also play a twillek, im a MTK now, so i rarely wear armor anyway, and when i do it's ubese. But i previously wore a suit of composite, with low enc leggs (took a hit on the effectiveness for it), and a mabari helmet to save my mind.
You CAN get your armorsmith to make low encumberance composite leggs... the qual/mal stats of the resources translate to encumberance, and the qual/UT? (i always confuse ut and sr) translate to effectiveness. When experimenting, armorsmiths almost exclusively go for effectiveness, as that's the best use of the experiment points. I've noticed the materials used also seem to lean more toward effectives rather than encumberances...
So your armorsmith should be able to make you some low encumberance composite leggs, though they may take such a effectiveness hit as to make high kenetic ubese leggs a better choice functionally (depends on the materials he/she has).