Hollis F2 "slightly" lighter than F1? I'd say significantly lighter--and a lot lighter than Jetfins. And the blade is small compared with the F1 and Jetfins. In the linked-to page Hollis touts the "power to weight ratio." While that might be so, I found the power to be insufficient to propel myself with heavy tanks. It is a fun fin for travel to warm-water locations where there is little current to fight.
If you're able to trim out in the drysuit without a heavy fin, and are amenable to something lighter, consider the Deep6 Eddy fin. I love them for wetsuit diving, but I use the heavy Jetfins for drysuit and double tanks.
If you're able to trim out in the drysuit without a heavy fin, and are amenable to something lighter, consider the Deep6 Eddy fin. I love them for wetsuit diving, but I use the heavy Jetfins for drysuit and double tanks.