Hi Anthony
The spring pans are a step in the right direction, I still feel the springs are a problem, The free length of the spring 14.25" the compressed unladen length 8.75".
When new the springs should give a 2" clearance under the bump stop,the car unladened so given that the Repro bump stops are on the large side, 40mm clearance is a best guess estimate.
The compound errors, spring length, is 6 mm (1/4") short, and the bump stop is too big,by,about the same, so 12 mm (1/2")is accounted for, and "if " the spring rate is incorrect( too soft) it all starts to add up to the problem you seem to have. Interesting situation.
Kind regards
Trevor