Set about making myself one a short while ago due to my sump being about 50mm off the floor (if anyone has any engine raising idea's, and a way to keep the prop straight, that'd be great!).
First off was a really thin sheet steel thing, that molded itself to the bottom of my sump, then started wearing through. So I stuck another piece of the same steel inside it, just so it'd last a little longer, and took it easier over speedbumps (now 5mph, diagonally, and still scraping!).
I got pretty pissed off with this, and went and bought a steel sheet from the local scrap metal place. Evidently it was someone's pride and joy (lol) at one time. A big sheet of 5mm steel that'd had various sections milled out. I used the template from the old sumpguard, except I made it squarer. Easy!
For the front mounts I already had 2 holes, so used those, but somehow had to get the metal to fit. To do this I cut 2 slots and welded 2 piece of metal in. The metal I was welding in was so ridiculously tough that it destroyed 2 8mm drill bits drilling 1 hole, so I gave up and cut more slots!
The 3rd mount is actually on the engine itself, see the photo's.
Its proven to be strong - I accidently lowered the car back down while there was 2 bricks under the sumpguard, and it just sat there!
I still want to raise it slightly, there's almost a 1" gap between the sump and guard atm, and this means I touch the road EVERYwhere.
The pics:





As soon as I've raised the rear mount a little, I'll be happy. Admittedly the thing is pretty damned heavy, but its worth it to never go through another sump on here! I'm presently on my 4th, to give you an idea! Its thoroughly offset by the lack of rear seats and stuff too.