Ride height and coilover setup

I've setup my coilovers recently using the method in this course and come up against a snag with the settings.

I run a mild wheel and tyre setup compared to oem (same diameter and width just a slightly lower offset), on the front I found I would foul on the inner guard after not much compression so I wound the damper out of the lower mount to stop the tyre catching. I did this until I was left with 25mm of damper remaining in the lower mount (I'm not comfortable winding it out anymore). Yet even still my tyre catches slightly on the inner guard.

I've ended up with having to set my ride height at a point where I have 35mm of compression travel remaining and 120mm of damper extension from ride height (jacked up the front suspension looks like a rally car with the amount of droop present). I've had to introduce a helper spring as I've wound the spring perch so far down that the main spring wasn't captive on full droop.

My best guess - I need a longer damper to achieve a sensible amount of remaining damper compression from my required ride height?

The rear of the car is the opposite of the front. I just about managed to achieve good clearance to the inner guard, again with the damper wound out to it's maximum from the lower mount. With the ride height set, I have masses of available compression travel - 95mm. Yet on extension I only have 20mm remaining. As soon as the car is jacked up a small amount the rear is in the air freewheeling (obviously no good on track as I will end up with 3 wheels on the track during most corners. It's basically the reverse to the front setup.

Does is sound like I have done something monumentally stupid? Or are my coilovers not suitable for the chassis? Any pointers to something obvious I may have missed would be greatly appreciated