I asked a friend who was a ChemE in college what I could do to make my CPU bracket stronger, he passed me on to Larry. Hi Larry!

Larry's suggestion was to add fiberglass threads to the resin as it mixed. My last interaction with fiberglass involved Tequila and the last football game I went to at OU. I woke up the next morning with a rear end full of fiber - seems I had worn shorts and somehow managed to find a spot that was flaking.

So I listened and got a tyvek jacket:

I also pulled out a mask I had used when painting our cement floor:

I also got some fiberglass cloth to cut into 1/4" strands:

I could go on about technique, but you cut at 45 degrees to the grain and you want shorted than 1/4" in. Anything longer (upto 3/4" in) you keep in a different container. I have a picture of my two containers, and yes, it appears both have strands longer than 1/4" in:

The other thing I needed was something to vibrate the mold to get out air bubbles. Try as I might, I couldn't think of anything. Except making my iPhone ring and ring. Or finding an app what made it vibrate. I paid $0.99 for some app and covered my iPhone in an expensive protective sheathe:

Here you can see my first run:

You can see the sandwich bag housing the iPhone, you can see where I added 4 holes on the feet to allow additional resin to be added. You can see I'm making a small plug to test strength.

And you can see I made a mess:

I didn't bother cleaning off the flash - the resultant structure was weak. I'm not sure, but I think I didn't stir the A and B compounds enough for the first batch. The remaining batches did get stirred and the final plug shape I cast was much stronger. I remember that the bracket felt like it had not set when I pulled it out.

We can see my sandwich bag was a good idea:

I did another run, not shown, and the resulting cast was stronger than both the first and the prior one without the fiberglass. But, I was getting frustrated because my resin was setting too fast, it was difficult to get the gooier mix of resin and fiberglass into the form, and I didn't want to recut the fiber.

I've since used milliput (and a nice clay snake!):

to extend one of the original brackets:

I'm waiting for that to set before I dremel it out.