Merlin asked me for my 2 cents.
When I built my first DIY Monofin I also thought of new materials, also Lexan. I also did some experiments with it, but it was too fraguile to handle the force you put on the blade with every finstroke.
So I decided to make the blade of resin and fibreglass like every normal fin. (also most of the carbon blades have a core made of fibreglass and resin).
Of course fibreglass and resin isn't really cheap. A DIY Monofin like this with OMER footpockets have total costs of about 70-100 Euro, depending on which materials you take and how stiff you want your fin.
Then you have about 5-6 hours working time, and the insecurity if the fin really works like you wanted it and if it's worth the effort. So Monofins from Specialfin or Leaderfins which costs 200 Euro (I don't know how much, but you can look on the pages) aren't very expensiv.
For instance, I tried to make a carbon-aramid-glassfibre fin. It was total crap. It looks great but what a crap. The bending was not good, and too hard. 70 Euros for a nice looking blade with no purpose of use. Too much in my mind.
But I find a good way to fix footpockets on the blade. First I tried a two compnents glue specially for rubber, forgett it. And the yellow glue doesn't look nice on the blade. Then I tried superglue (normal superglue from the market) this works, but don't use it economically. Take a lot of glue.
The best is the same resin as I used for the blade.
If you will use OMER pockets use the screws on the downside.
If you would like to know what material I used for my fins look at
www.r-g.de
-epoxy resin L
-hardener EPH 161 (VE 3261)
-EP gel coat colourless (for the last layer on each side of the fin, you can also colour this)
-glass filament fabric 80 g/m2
This you will need for a normal mono. But you also find the other things like Texalium (I used for my second mono, it's a aluminium coated fibre, for metalic surface)
and also the carbon aramid fibre.
The next fin I'd like to make is a glass - aramid fibre fin, for Dynamic (nearly straight with open heel footpockets). extremly lightweight and thin, but the same bending and stifness as my second fin (the Texalium thing), I hope my calculations will be right.
I sure will put some photos and a detailed report on deeper blue, if some are interessted. But you will have to wait one or two month until I will have some time to spent for planning and constructing.