I thought you may have done that conversion as I always had too many bases so I never tried adapting the rear discharge full crank steel base, good to know it's an option.
I think there should be a solution to the leaking needles ,I know you could test for problems before fitting the cap by turning the cap upside down and using a pressure tester.
I'd think it can only be a cap or float problem because all the old caps work well.
Send a prepaid small plastic bag (under $10 for a bag that takes up to 5 kg) with problem caps , needles and floats to CM for testing as he can pressure test them.
