So you already have the HVH/NX Super Sucker blended spacer with integral nitrous lines ? If you do, do not run any spacer over this and do not run a super sucker or other 4 into 1 blended (or 4 hole for that matter) spacer underneath it !!!! A 1/2" or 1" open underneath it will be fine if you want more plenum volume. Just make sure their are no ledges at mating of both spacers.
You do not want to go from open to 4 hole no matter what the circumstance !!!!
i don't have the hvh/nx plate, just the 2 stage twin gemini plate with the old school bars(it has 3, 1 centered, and 2 on the outside).keithsvt got me a smoking deal on the 1100.00 kits, he beat it by ALOT