Also, Galaxy, hybrid silicone tails exist :)
They're made with stronger monofins meant for deeper diving, such as finis foil, finis rapid, etc. and they're neoprene coated in silicone. It's not as heavy as regular full-on silicone, so that might be a good option for you!
They're also on the cheaper side, usually around $200 - $500 ~
They're DEFINITELY faster depending on the tail's fluke shape. Anything is faster than a FinFun monofin !
The only two makers of hybrids I'm aware of is Mermaid Mazu and Purple Mermaid Stuidos! Click their names below to see their pages:
Purple Mermaid Studios
Mazu's Mermaid Emporium
I hope I'm helping! <3