I got a cheap SUP, and have tried it a few times in the river. Honestly, I don't really enjoy using it as a SUP as I find the whole paddling thing as too much effort compared with holding a sail! Unfortunately this Anaconda model does not have a sail nut insert so I thought I'd add a mast track.
Here's a perfectly good SUP about to go through surgery
A 10" Chinook Mast track was purchased from Stuart Bell Sails ($30) - I decided on non-vented version as the SUP already had a vent in it. This looks like as good as any location for it - no science involved
Take a deep breath, and start the router. I read a lot of information about setting the track into divinylcel or some other hard materials before setting it into the board. I chose to ignore this advice because I couldn't be bothered, couldn't find the stuff, and decided that this won't be used in any more than 8 knots of wind on flat water. Time will tell I guess
Resin and 6 layers of fibreglass were laid down, then sanded.
New grip added, and it all seems to come together
I had a quick try of this with a 5.3m Severne and it appears to work quite well. The wind was a very variable 1-5 knots and changing direction. I did find it hard to go upwind. I tried railing the board a fair bit but still struggled to get back in the offshore wind. Maybe next is a fin box underneath for a centrefin

. Or maybe it just needs more suitable tail fin.
If anything, at least now the board is dual use and my daughter will be able to uphaul on it far easier than on my Kode 122 ltr.