Hello,
I use aluminium lips on about 90% of my cankbaits. Only the
small crankbaits get plastic lips. I use 1,5 mm Alu sheet.
Don't sharp the Alu Edge!
The advantage of Alu is that you can bend it easily,
even after mounting, to correct the walk through the water.
The extra weight is no problem for most of the baits. If you
want even more extra weight (for divers) you can use brass.
Visibility: The fish really don't care at all....
Best regards,
Christoph