Peter,
IMHO - 'sagging springs' won't help with the bottoming or the handling, but I'd tend to think of the shocks as damping out the natural spring response in transient/transition. If the springs are 'weak' then you can 'dial out' the initial response on turn in or over bumps. But, if you go too hard on the shocks (too many clicks), because they don't have separate bump and rebound settings, you could go too far and end up with the the suspension 'jacking down' over a series of bumps. So, you need get the springs right first then play with the shocks.
Re the loading on the springs, I'm the 'new boy' here and don't know what the max loading should be, but surely someone on TM will have the knowledge. However, didn't Morgan change from 5 leaf to 4 leaf springs (for comfort?) circa 2005/6? Maybe if you prefer a firmer ride and need to keep the ground clearance up, you may be able to ask them for a change to the earlier spring setup?
