Is there a quick / easy way to create your own (not protuding beyond the flange)? Have router but have never made a HD foam insert. Would be easier if Futures provided the aforementioned but I doubt that’s ever going to happen.
I have got an old O’fishl jig that I use to rout my hole for my HD foam insert. Then I razor cut or band saw a piece of the black HD foam to fit that routed hole. I glue the insert into the hole using Epoxy Resin (slow). Just enough on the bottom and side to make it stick. No excess. Lightly sand if necessary. Once that has set, I rout my Futures box, install and continue glasssing the bottom. If done right, it gives you a nice uniform insert. Haven’t done one of these in a long time. I may have to do one for purposes of illustration.
^^^^ That’s one way to do it. Another way to do it is the way some of the Compsand guys were doing it. They installed the HD insert into the blank before shaping it, even connecting the insert to both the deck and bottom. Then “glass” as normal (which in their case included the wood) and do the fin system install last.
The variation from that which I’ve done is to lay a layer of 6oz on an HD panel, cut inserts out of that panel and install them into blank before shaping, but only ~1" deep into the blank and with the glass side down. Then when you install the finbox there’s a layer of fiberglass at the bottom which adds to a truss-like support for the box at the bottom as well as the top. That box will never roll. It’s overkill when using a fin system, though; I mostly only do it to support a rout-in fin install where there is no finbox. .
The method McDing describes above is less complicated and is plenty strong for the application.