Not sure what the outside body diameter of the 8NX is. You may want to buzz by:
www.mountingsolution.com/.
Not saying do not mount it, but along with Al's comments, a couple of other things to consider before electing to do so.
NiCd (what is currently powers the 8X series) batteries are generally not as reliable as a lithium batteries.
1. They self-discharge over time. Leave them alone and you will come back to a dead battery. Approx 20% loss per month. 3-volt lithium batteries retain 90% of thier energy over a 10-year period.
2. The more so as they go through their duty cycle of repetitive charge/discharges the less efficient they become.
3. Running them to zero can lead to damage in the individual cells that make up the total battery.
4. They can be damaged by over-charging in non-intelligent chargers.
5. Discharging NiCd batteries in weather below –4 Fahrenheit will lead to deterioration in battery performance. In other words, damage it.
6. If you have kept up with other SF battery threads around the net, you will note quite a few problems with some lots of SF NiCd batteries. I think they have resolved this problem, but the other day I had to discard a SF NiCd battery after first use out of the wrapper because it would not hold a charge.
7. NiCd batteries will “suddenly” drop in power and leave you with no light. That is constant voltage….then DONE with little or no warning. 3-volt Lithium batteries will run, then begin to “yellow’, then continue to provide useful light for a reasonable amount of time, then fade into non-usefulness. A rule of thumb for me is, if I am asking myself, “Is this light as bright as it should be?” – It is time to change the batteries.
All that begin said, I ran a customized 9N for quite a few years on a training weapon. It had a tape-switch and a 3” Turbo head. It was fantastic for training purposes. I used high-speed low-drag electrical tape and electrical ties to secure the thing! All my duty weapons have non-rechargeable lights on them.
Not sure what the shock-isolation story will be on a 8NX either. A weapon with decent recoil might be problematic. An AR should be OK.
As far as batteries, Lithium Ion rechargeables should be a slightly different story.
Here is an excellent primer on batteries (more than you wanted to know!)
www.extremetech.com/article2/0,3973,17631,00.asp