Grids ??

Hi all, 
Having really hard time figuring out what to do about the grids.  Our layout and size does not match anything in the books or on this forum.  Does anyone have anything similar to help figure out what type of Grids to put in? 

This photo is an older photo shows cedar beds under construction before Mel's Mix was put in.  There is 16" of topsoil shown in photos.   We are planning on putting "caps" (2x4's and 2x6's)  around the top edges of each bed to enable us to sit on while working in beds.   The caps won't allow us to screw in the grids so I guess we'll have to lay them on surface of Mel's Mix.  You can see the perimeter beds are 20'x2' on north end, (bottom of photo) and 40' on East and West sides.   The (4) middle beds are 4'x8'.  They are all 24" in height.  

The choices I'm considering for the grids are very thin PEX pipe  held together with connectors or maybe machine screws/bolts... have to check out Home Depot today .....  or 1/2 x 3/4" wood held together with bolts & screws... both layed  on top of the Mel's Mix.   

For some reason I don't like the idea of string which requires putting in screws all over the place to hold the string.   

Is there less risk of bugs gathering under the PEX then under the wood?  Does laying the grids on top of the Mel's mix cause any negativity in the growing process?   

Thanks in advance for any advice, 


Alan from Asheville. 

P.S. the male in the photo is my neighbor helping with the build and the lady with her back to us is my wife

This worked nicely for me, only weights kept grids straight. Also were very flexible.

I was in the process of looking for old window weights to use, it would have been much more streamlined... large fishing sinkers could also work..

Alan, one option you might consider is to make notches (groves) in the top of the frames every foot before putting the caps on them. Then pull the clothesline through the notches with weights as Jimmy shows on his.