If they are still a little to soft, you could try boiling them for a little longer, that would harden them, you could also leave them out to dry in a mesh bag.
I wouldn't bother hooking them directly as hair rigging works so well.
Some 10mm boilies can split easily when using a baiting needle. Try making spikes from old hooks by snipping off at the bend and tying this on the hair. The mini boilie can then be spiked on the end without splitting.
Not so good for a long time wait for bites but 10mm boilies are not anyway. The small fish can demolish them easier.
you could try drilling them put the hookbait in pva mesh so has to hold it together on the cast and use a fox pellet peg instead of a ordinary stop.or put in the arma mesh and smoother it in paste made from some ground up baits.
clive.