Hello Ron,
Firstly, I don’t have any experience with PHD, sorry!
However, from 1997 to 2003 I did regularly battle with my own LX200 and faced the same dilemmas as yourself, except that I also had huge non-Go To Newtonians at my disposal.
I initially used an SBIG ST7 with a built in autoguiding chip with my LX200. The arrangement worked, BUT, was always a hassle to set up. It was far less stressful to simply take multiple 60 second (or less) exposures, especially as I mainly imaged comets that moved in longer exposures anyway. Mind you, I was never a mega-long exposure Deep Sky imager anyway. As well as comets I imaged novae, supernovae, and other objects for which a set of 60 second exposures was good enough.
My biggest problem though was with the LX200 itself. On the 2nd night of use the RA motor/gearbox failed. This was soul destroying on a brand new £5K instrument. Eventually the dealer replaced the entire telescope, but the problems continued. Once or twice a year the telescope had to be dismounted and sent back to the dealer for new motors to be fitted….. This went on for 6 years. I examined the motor/gearbox assembly and was horrified to find a (literally) Scalextric toy car motor providing the drive to the gearbox chain; the gearbox consisting of tiny plastic wheels, glued onto shafts before the final worm stage. It was this gearbox/encoder system that always failed. On full slew the motor spun at 14,400 rpm (gulp!)
After I found this out I never slewed the telescope again, just synced on a star and crawled to the right RA and Dec, or unlocked the axes and pointed the LX200 manually. Eventually I gave up and simply used the LX200 for planetary work. But I dreaded even going outdoors at night for fear of the drives failing yet again. I bit the bullet and acquired a Paramount ME & C14 at this point (2003) which has never let me down. I temporarily remounted the LX200 tube on an EQ6 but this was not a brilliant solution as the 12″ tube was a bit too heavy (your 10″ will be considerably lighter though).
I’ve gone off topic here and not really answered your questions Ron, but, suffice to say, with my own LX200 the only way I could use it without loads of night-time hassle was using multiple short exposures and never slewing at high speed. There was not enough time between breakdowns to enjoy using the system and to perfect autoguiding. Eventually I grew to really hate the telescope with a passion!
I guess what I’m saying is, a decent modern mount really is the best solution. Even a humble NEQ6 Pro is in a totally different reliability and stability league to a vintage LX200. It’s like the difference between a BMW 5 series and a Morris Marina!
Hopefully someone else can answer your PHD query.
Good luck!
Martin