Personally I'd go with an aluminum plate. They weigh around ~2lbs depending on the brand. A Halcyon carbon fiber plate is around 1.1lbs. A pound is a pound. Most of us can deal with being a pound overweight but then again every little bit helps.
If you can get a set of LP85s and do a modest overfill (commonly called a cave fill) they will give you much more gas than a set of AL80 doubles. LP85s are my favorite set of doubles and sidemount tanks. Even if the shop is only willing to fill to ~3000psi they're basically like HP100s. Unfortunately not every place is willing to do this.
~3600psi/2640psi x LP85 = ~115cu/ft / z-factor (1.0491) = 110cu/ft x 2 = 220cu/ft
This is splitting hairs and I'm sure someone will come along shortly and correct my math but all things considered a cave filled set of LP85s holds around ~220cu/ft vs. a set of AL80 doubles at 154cu/ft. It's almost 3 AL80s worth of gas.
Generally speaking I don't like diving steel doubles in a wetsuit but I'll make an exception for LP85s.
If you can get a set of LP85s and do a modest overfill (commonly called a cave fill) they will give you much more gas than a set of AL80 doubles. LP85s are my favorite set of doubles and sidemount tanks. Even if the shop is only willing to fill to ~3000psi they're basically like HP100s. Unfortunately not every place is willing to do this.
~3600psi/2640psi x LP85 = ~115cu/ft / z-factor (1.0491) = 110cu/ft x 2 = 220cu/ft
This is splitting hairs and I'm sure someone will come along shortly and correct my math but all things considered a cave filled set of LP85s holds around ~220cu/ft vs. a set of AL80 doubles at 154cu/ft. It's almost 3 AL80s worth of gas.
Generally speaking I don't like diving steel doubles in a wetsuit but I'll make an exception for LP85s.