In my experience, using the Girdle band alone doesn't ensure you have a proper seal. Putting the band around an OPEN case and tightening it could potentially put uneven pressures on the flanges, and might even warp the band. You may even find it very difficult to re-mate the band's nuts & bolts if the filter top isn't fully seated. It's just my opinion, but the girdle band "Holds" it together, it doesn't PUT it together. Others' opinions may differ!

Just incidentally, here's my steps for a DE filter cleanout.

-Backwash per normal.
-Shut off the power at the breaker or master cutoff.
-Open the vent valve at the top of the case (your pictures don't show one? Where is your air purge vent?)
-Remove the girdle.
-Remove the lid. Keep in mind that the filter is still FULL of water. You're going to get somewhat wet. You want the weight of that water holding the filter in place. If you can manage to drain the filter BELOW the girdle, that's fine, but I've never managed to get it just right... Stand back, it'll be messy and smelly.
-Remove the bung at the bottom of the case slowly and set it aside.
-Use a permanent Sharpy marker to mark on the PVC standpipe how far down the filter assembly mating point is installed over the pipe.
-Lift the WHOLE Grid Assembly out as a unit, sliding it off the standpipe, being careful not to torque it or twist it because the manifold on top can crack. You might enlist help from someone as it can be heavy (30 or 40 pounds?)
-Remove the wingnut from the top of the manifold and put the washer and wingnut in a safe place. They're easy to lose in the grass. If you lose one, buy a replacement stainless steel one at Lowe's or Home Depot, not a pool supply unless you have to. Home depot is about 10% of the cost of Leslie's... The guy at our neighborhood Leslie's even told me the exact size and to go across the street to Lowe's.
- Turn the assembly upside down and remove the threaded rod and set it aside.
- Take the baseplate off and set it aside.
- Remove each grid by lifting it STRAIGHT OUT of the manifold.
- Clean each grid with a garden hose power sprayer.
- Inspect each grid carefully for tears or holes. Replace any that are brittle fabric or have tears. Even a tear 1/4" long can cause DE to enter your pool and reduce filter efficiency. I usually wind up replacing one or two every year.
- Clean out the standpipe fitting on the manifold making sure to get out all the old grease and dirt so as to not allow grit to erode the o-ring gasket on the standpipe.
- Reassemble in the reverse order, again doing it upside down. Take note of the indicator on the manifold that indicates where the "SMALL" grid should go. You'll note that one of the grids is smaller than the others. It's smaller to make room for the standpipe.
- Put the baseplate back on, and CAREFULLY reinstall the threaded rod from the bottom to and through the manifold.
- Turn it back over and reinstall the washer and wingnut just barely finger tight.
- Remove and clean the standpipe o-ring. Re-lubricate. Don't be too miserly on the lubricant. Replace the o-ring if needed.
- Reinstall the assembly onto the standpipe, observing the depth you marked earlier.
- Remove the rubber o-ring from the filter case. Clean it with paper towels to remove any grime, old grease, and grit. Do the same on the case flanges.
- Re-grease it as described above.
- Set the filter top back onto the o-ring, and using downward pressure, re-seat the lid.
- Replace the girdle band and tighten until the spring coils touch each other, then about 1/4 to 1/2 turn more.
- Remove the valve stem from the vent valve. Clean and regrease the o-rings.
- Check the bung o-ring and re-grease it. Clean the bung and bung hole (yes, I know...). Replace the bung and tighten.
- Turn power back on, then turn pump on until a steady stream of water is emitted from the valve opening.
- Turn the pump off and re-install the valve stem, but do not fully close.
- Turn the pump back on, and wait until all air is purged from the filter case.
- Close the valve.
- Recharge with the filter with the correct amount of new DE.

Voila! I've done this about 20 times on my filter (once or twice a year) The first time took several hours. Now I have it down to less than an hour, with the longest time being the inspection of the grids.