Thanks, Rog, for your kind comments!
First off, I have to say that the original inspiration came from Roger Dodger Aviation; I just used their free video to copy the design.
It's a great idea, and I've adapted it to suit my 'special needs' And it is probably the only version built by a one-armed bricklayer!
I did consider solvent welding but settled instead on using short, bolt-headed, self-tapping screws. They conveniently fit the standard magnetic tool-holder that goes into my battery-operated drill, and the design includes a hole-cutting tip on the screw. So it was a bit of a doddle to set up in that way. But cutting pipe one-handed was a nightmare, even using a sharp saw and a work-mate to grip it. I persisted at it and even learnt a quick way to remove swarf from the rim of the cut tube; using one of the holes in the work-mate's deck, rotate the pipe at 45 degrees so that the rim contacts the edge of the hole and grinds the swarf away. Easier done than said!
All in all I was glad to have resisted the call to glue it up. Trial and error doesn't work with solvent welding, and with fittings about £1 a throw I couldn't afford to screw up. The self tappers pull the whole thing rigid and allow for retries!
I will take a shot later that will show how easy it is to climb into the new 'pit. It's all designed around the standard rolling, rotating office-chair. The pilot rolls into place and then straps the chair to the frame, usefully preventing further rolling or rotating from the chair. It's as comfortable as any of the specialised pits I've used before, and possibly the best.
I'm off to paint on the last coat of grey. The 'plumber's nightmare' is squatting menacingly in the centre of my room, looking mean and businesslike.
cheers!