I stock cams with a smaller base circle however that does not solve your issue fully. You would need to add a 2mm washer also under your springs to bring the spring pressure back up.
Replacing the seats and doing it correctly is the right way of solving this
Might not need 2mm of spring spacing, maybe not any. The double spring setups put the spring force around 130-150lbs installed, they really need to be around 70-90 unless you're running serious revs and a big boi cam.
Good stock springs and an IPD turbo cam are good for at least 7500 rpm.