Cooper S front bags have about 10mm more thickness in the rubber cone above the bag.
Rear helper springs are the same as yours.
I have S front bags and stock rears in the wasaMatic and it sits level with 2 full tanks.
To level yours a bit the correct method is to fit a washer on the front knuckle joint pins. I think 4mm is recommended maximum.
Edit
All hydro cars were higher in the rear by design. But it gets exaggerated with age.
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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
