That's a good one! I think (and this is my opinion) leave 20 degrees of flap and sideslip, as you have the option to come out of the slip and slow the descent again. Once the flaps are down then it is it! You're absolutely committed (I know you're committed anyway - but you take away options)
Once you have corrected the height you can then resume normal service, so to speak... and drop 30 for touchdown.