What size cells does the N30 have?
11 3800mAh Sub-Cs.
The L35 will be, IIRC, using LiPoly cells in a "brick" configuration. This will allow tighter packing and more energy density than a similarly sized bundle of 18650s. I'm not sure if they'll go for a 3s or 4s, that would depend on the operating bounds of the HID ballast. For 4s LiPoly to work, the ballast will need to tolerate as high as 16.8V. For 3s LiPoly to work, the ballast would need to tolerate as low as 9V.
I actually don't even need all the runtime on my N30 as it is, so there isn't much incentive for me to attempt to "homebrew" a LiIon upgrade for the N30. If I was going to do that mcuh work, I'd probably want to cannibalize the entire light for the ballast and bulb (and loose sub-C cells), and find an entirely new host for it.