Kreg Jig HD - 4x4 rails

[John Horrigan]

Good morning to all from a Kreg newcomer. 

I'm in the process of constructing a stand to support at torsion box, that will in turn hold a CNC router (30 x 60 table).  I anticipate significant racking force from the CNC machine, hence the torsion box to isolate the stand from the machine. 

I've looked at a number of joinery options for the stand and have decided that the simplest approach is to use 4 x 4 pine with kreg HD joints (and glue) , with 2 x 4 cross pieces and corner braces to deal with the racking.  First question: Will these joints stand up to racking?

The second question: - Looking at the rail strength article, it looks to me like the best approach is to have 4 pocket holes per 4 x 4 joint.  The issue I can forsee (will be testing on scrap shortly), is that if the long and short rails mate at the same height on the corner leg, the inner pocket hole screws may come very close to one another.  Does this pose a splitting risk?

If proximity of screws is an issue, one option that I have considered is using Kreg HD joints on the outside of the rail, but use my standard Kreg jig on the inside, so I can get away with shorter screws.  Is this necessary?  Would it create more problems than it's worth?

Thanks for your advice.

Cheers

John in Ottawa, Canada (wind chill -35C)