Okey dokey mate - I just didn't want to bore people to death! Here is what I wrote to Ender about fixing them beyond the previous post (pun intended) - I have left out the parts about the man-love and bromance, and where the two of us go from here....!
I get what you're describing - I think you have the main issue though, leaving the curtains up.
If I'm honest, with the height of the poles, I'd definitely go deeper, to two feet, and probably make them wider but straight instead of pyramid shaped. I realize why you went for the shape you did, but it seems vertical and wide does the job.
In terms of compacting the dirt, did you compact below the post? Really tamp it down hard, very very firmly, then add a couple of inches of gravel. When you pour the concrete on this, it binds the gravel and works like a huge bunch of fingers gripping into the dirt beneath, but the gravel stops any standing water from eating away at the footing if you see what I'm describing.
So the idea of bolting the poles to the footing is fine, no problem at all - make sure to leave a couple of days after pouring before putting the fixings on though, just so it has time to set and settle, as the crystalline formation takes longer than the setting appearance suggests.
What is the gap between the bolts? Presuming they form a square. This is the measurement to triple for the width of the hole. Ie a 3" bolt gap should give a hole 9" across. Square holes are much stronger too from the corner shape giving better bracing. Hire one of those hole digger tools if you can (rabbit holer, or post hole cutter - they have two shovel faces facing each other that grab the dirt) as it really helps your back when going deeper. Then square the hole with a normal shovel and use the rabbit holer to remove the crap. You can hire tamping poles too for firming the base, but a bit of heavy wood on a pole is cheaper to make!
So that is the main advice mate. Getting the depth, width, and sturdiness of the base below the concrete pour is really critical for long life. But reducing the drag from the curtains is clear too as you said - but that's already obvious to you!!
Hope this helps anyway, and as above I won't be offended if you don't want to do this - I just wanted to pass on the tricks that were passed to me
Ps - you'll probably need more concrete mix too. Get the ballast portion right as if helps gripping the sides, but always give it a little time to set well before attaching the bolts, so they don't cut off and smooth the concrete around the threads. Get a good length bolt too obviously!
You can cover the concrete top with dirt, turf, gravel if you want, but that's aesthetics. Just go for a good depth.
Let me know how you get on buddy