I am totally in agreement with Tobin and StefinSB. If I were to go on a dive vacation, I will bring my optimal gears for the environment, weight saving will come from non essential items. If I need to pay $50 for additional weight, so be it. After all, what is $50 compared to the cost of a dive vacation.
But really, AL/Kydex vs SS, there is only 3lb difference. Assuming you are off to a tropical location, I really don't think I need 50lb worth of stuff. Last time I flight to Thailand, I had AL plate, Oxcheq 40lb wing (not the lightest), SS STA, cambands with SS buckles, OMS slips with spring strap, LM 9A battery & charger, DRIS3C backup light with batteries, small camera setup (Canon S95 & Gopro), boots, hood misc trim pockets, highland shorts, SMB .... + personal items (tooth brush, sun screen, clothing ..) . The only things I didn't bring were wetsuit and weight. The whole thing with the suit case is well under 50lbs. I was packing in rush too, if I had more lead time, I could have save some weight.
The only time I went over 50lb was for a cold water destination where I also brought alone drysuits, 400g indie, jets fins. More clothing too because of colder top side. And yes, I did pay over weight. But I was well over 50lb. Saving 3lb plate won't help anyway.