Can't quite read the photo-credit - but I hope he/she doesn't mind!
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Last year's maters (early season):
I even grew CORN successfully in them, one year. (and I have NEVER gotten edible corn from my garden in the past).
Every spring, I dump last year's soil into another bed (that I'm trying to build-up) and I start with fresh organic garden soil (giant 3 cu-ft bag from Home Depot - although I can't remember if it took more than one bag for all three planters). I amend with steer manure (also Home Depot) and compost (from my compost pile). I did experience a little blossom end rot on some of my maters last year. I've been saving/crushing egg-shells from The Girls. I'll add that to my 'Mater Mix this year...
The cages don't fit inside the planters, so the bases extend beyond the width of the boxes, and I tied 'em all together with extra garden-stakes and twine (the garden stakes go clear to the ground). It was a very sturdy support system! Alternatively, I think gardenpatch sells trellisy things that "fit" the grow-boxes perfectly. Can't comment on them since I don't use 'em.
If I wanted to get SUPER-CRAZY, I'd rig the thing up on cheap movers-dollies so I could move it around to maximize sunlight thru the growing season (yah - NO!)
All told, the initial investment was pretty hefty ~$100 for 3 planters and - I think I paid appx $50 (on-sale) for the cages. But since it's been soooo successful (very ample harvests over 3+ years), I think it was money well-spent.
As for Super-Squirrel... Maybe try some bird-netting draped over the cages? Not sure if that would be 100% squirrel-proof (and the plants will probably try to grow through it anyway). Alternatively, maybe Google "Keep squirrels out of the garden" for other ideas. I saw someone suggested cheap pinwheels as a squirrel deterrent (Maybe? I actually do have some shimmery pinwheels in my raised beds - just 'cause I like cheesy, colorful crap in my garden beds - and I haven't had any critter-nibbling - never realized that the pinwheels were an actual deterrent!)
Ehhh... That's it for my Brainstorm this morning.