Personally, I wouldn't do the batten thing.
First off you'll want the vice for something in the middle of drilling and cuss roundly.
Secondly, it won't be stable anywhere other than hanging off the edge of the bench. So when you come to move it you may have a problem.
If you can find one of the
cheap portable vices that look like this:
They're actually pretty strong. There are several sizes though, so beware - the small ones are really rubbish. I have a couple of the 610mm (24") wide ones -- I note there's an 800mm version too -- and they've served for many tasks.
Check the strength of the legs too, though. The ones on my two good ones are 30mm box section steel, but I bought a cheap one from Toolstation, thinking it was the same, only to find it was "miniaturized", basically scaled down - smaller, a lot lighter and particularly weedy legs. So there are good and bad ones out there.
One was my router table for a couple of years (open wide, unscrew the jaws, replace with a single slab of MFC with the router in the middle). One is usually the mounting for my Kreg pocket hole jig, and one serves as the bench for my cast iron A3 printer's guillotine (which is so heavy I can only move it around in three pieces). I could make good use of two more of the good ones, any time*.
They used to be dirt cheap - less than 20 quid, but are probably a bit more now. [edit]
I've just looked at the Amazon reviews for this particular one - some people say the steel is too thin. I note there are really cheap versions out there that look similar to the decent ones. Check what you're getting, if you can.[/edit]
For big things, just open the jaws to maximum; mark, drill and bolt through whatever you want to fix down. If you're worried about stability, you can even drill into the legs and add extra braces, but I haven't found that necessary. Replacing the MDF top with ply gives extra strength, but I haven't needed to yet. You can flip them over, too when the top surface becomes worn, cut up and paint spattered.
Every home, er workshop, should have one. Or several. See the late and much missed Niki's postings -- he had a slightly more posh design (tilting table), which he also used for a RT. Best 20 quid you'll ever spend on a tool, but get two as they're excellent trestles and saw horses, etc...
E.
*If yours came like mine (and the picture) remove the four bolts securing the legs to the vice mechs, and rotate the vice pieces 180 degrees (swap over front to back), so that when folded, the handles fold up to the top, not down onto the legs - they fold more neatly and it's easier to do with one hand and one foot!
