I recently upgraded to a D800E and 14-24 along with the Lee SW150 filter system. I previously used the standard lee system, which could handle three filters without any issues. The SW150 has problems with reflections when using multiple filters, due to the large open areas at the sides where light has no trouble getting in behind the filters. Lee recommend using no more than 2 filters with the sw150.
Here is an example of the reflection issue:
Here's a pic of the supplied baffle system:
I've been working on a better baffle system that doesn't allow any stray light to get in behind the filters. This is just a prototype so its a bit rough, I just used materials that I had lying around. Once I've finalised the design I'll look at getting it laser cut from aluminium and black anodized to match the holder.
The main bit is 8mm mdf, with 3mm soft foam attached to the front:
I used a bit of rope to fill in the gap at the back:
With a filter inserted:
I added a third slot to the holder, I took it off my standard filter holder. The longer screws can be hard to find, the thread is different to the standard holder.
I've tested it with 2x 3 stop and 1x2 stop filters stacked, which has no reflection problems. Hitech make a 10 stop filter to suit this holder but I dont have it yet to test but I'm confident it will work.