DIY Flexi First attempt.

Brian-
On a couple of the racks I have done, including one that is supporting a 350lb turntable, I drilled 3.5" in from the front and back edges, and 1.5" from the sides - to the center of the rod. If you want to go to 3/4 as some suggest, you may need to adjust slightly.

A good rule of thumb is to keep in mind what will be housed on the shelves, and keep a minimum clearance for standard 19" width components between the rods/nuts/spacers....

I build a two Salamander Archetype clones flexi-racks,and I wasn't happy with the results,the flexi-racks were unstable and wobbly.Here is my suggestion.The distance of the hole from the edge should be double the hole diameter.Go for 1" or 1"-1/4 rods brass or stainless steel.The shelves could be 2" or thicker maple,for hardware get a machinist to turn some donut shaped brass fateners instead of regular "nuts".See the Mapleshade Samson rack for inspiration.Yes it won't be cheap but quality never is.
Regards
George

Correction above " read FASTENERS instead of fateners"LOL
George

Thanks for all the help guys.