Hi Jon. I used this setup for an initial flattening of my new(ish!) workbench recently. First time doing anything like that and a bit of a faff to set up on my own but it worked really well. I bought the 4mm box section to make cramps. I kept two lengths back for future use for extra long cramps and of course they have sat unused ever since...
The jig sits on these obviously, and after some initial fettling the flattening was fairly mundane but it worked.
To flatten now, I modified the jig somewhat and the bars now sit on
top of the bench on either side with cramp at each corner to hold them in place. By adjusting the jig height I can dimension
relatively thick and thin bits of wood fairly easily. I will build a more easily adjustable and improved jig at some point and you wouldn't being doing it this way if you were making money from it, but it's fine for my needs. A bit of lateral thinking goes a long way. I was about to change the jig 'legs' a while back and stopped. Put a bit of scrap mdf under the wood instead and some double sided tape. Tadaaaa.
Trying to save money and used a straight bit that I had but now that I know it works I think I will invest in the Wealden one at some point when I have enough Overtime Points stacked up to justify it.
https://www.wealdentool.com/acatalog/Surfacing_6.html
Cheers.
Chris