I can't find angle iron at the DIY stores greater than 2", so I'm back to a 2X4 on the bottom to get the proper height. I think this might be OK since the slide "rests" on the inside bottom of the angle iron, and the wood provides support for the fiberglass bottom.
The angle iron is quite thick steel that I can bolt the slide rail to, then 5 large bolts through the bottom side of the angle iron, through the 2X4, through the cargo bottom, then to a steel flat bar underneath.
Since the depth is only 20" / width is 32", the guy at Rockler said this will work for a max. 150 lb. / 20 inch extension.
I appreciate the offers of assistance but can't make it away from work. Just took 2 weeks off. Hopefully I'll get this done before mid-july when we take off for SD.
If this configuration is an epic fail, I can live with that, then hopefully these offers stand for the future when I have more time. My main concern is not damaging the fiberglass cargo bottom. Everything else can be re-done.
(Sorry for the poor picture that is not geometrically accurate. Years ago I failed keeping the crayon in side the lines.....)
As I've said, this type of "designing" is not my strong suit. If you see anything here that makes you laugh or cry, please let me know..
Thanks all!