Just had a thought... But don't know if it's a crap one... If you have leaking splits and are to lazy to split and re-seal etc... Could you just stick some shitty tyre repair stuff in there??
ok so being lazy... guessing id have to cut all the old sealent out first? then run some back over the top?
Clean the old stuff out the join. Rub join down with 180/200 grit paper. Then use tigerseal/silkaflex/serious stuff around the join and let it set before mounting a tyre. This worked for a number years with my 3pc wheels which used to leak like crazy.
How are splits actually sealed 'properly' out of interest? Is there like a rubber gasket type thing between each piece or is like silicone that's applied wet and then dries?