I plan on using my optimus on a Tavor. The Tavor has a jam nut that is employed to secure a muzzle brake due to the long threads. I have read some things that state not to use it and some people that say its ok. At this point I wanted to use a minimalist brake on it. What do you suggest the best mounting option is?  What if I go to a 3 lug? Will the 3 lug mount employ the same rifle mounting option?

Im also going to be using it on a 300wsm. Is there an accuracy difference between using a direct thread or a taper mount? Will I be able to have repeatable POI's with the taper mount?

Am I able to use a direct thread piston and a fixed barrel spacer for shooting from a 556 rifle? Also, is it ok to use the 556 end cap any time I am shooting 556 or should I use the .30?

Are there any options to using another fixed barrel spacer in the optimus? Nobody local seems to have one in stock.

Thank you for your time.

This is what you need for the Tavor.

http://www.capitolarmory.com/tavor-muzzle-shoulder-ring.html

Griffin Optimus questions are probably better suited here.

I've read the 5.56 end cap is best suited for .22. I'm not sure if that's correct or not and 9mm end cap for everything else. You can use the piston on .22 cal rifles and hand guns.

There will probably be a poi change when you take the can on and off. The Optimus isn't meant to be a precision suppressor. You want to make sure you align the baffle stack the same every time to minimize poi change.

I've used the .22 endcap with .223 without any issue, but usually just use the 9mm cap since I'm frequently swapping the suppressor around.  Suppression works pretty well on .22 with either cap.

The baffle stack is "keyed" so you can make sure they all stack neatly together in the same orientation.  I haven't used mine enough to determine POI changes based on different orientations of the stack.

Same here. 
No issues using the .22 endcap on .223. 

What length are you guys using,is it worth while to get the mid length? I have shot my Optimus yet.

Yes! It's worth getting the blast shield for the mid length. 
Thats the only way I run mine on my rifles. I've never had mine in the full length config. 

If I recall correctly they only recommend using the .22 end cap in the short configuration. If you go to mid length, with the blast shield, or full length I believe it says to use the 30cal end cap.

Just got mine so still learning and spending money on extras. It adds up quickly!

from another thread in here.

They later came back and said it's fine to use the .22 endcap in the other configurations 

thanks I am new to this so spent 10 months ready! LOL

If I dont move the baffle stack and I use a taper mount, will the POI generally stay pretty close to the same if I take the suppressor on and off?

Yes.

I haven't had any problems with the POI shifting from taking it off an on. 
And I use it more on my precision rifles then anything else. 

About a month ago I did a test to check repeatablity of the POI. I took out the blast baffle and put it back in the same way each time and POI didn't change much at all.
Griffin said for best results line the notch in the blast baffle with the notches in the main tube.

OP I hope you do not mind me asking a question.

Has anyone fired .22lr through their Optimus in a longer configuration that uses the extra blast baffle? Curious if on a 22lr rifle if it would make it any quitter?

The only way you could do that is either with a .22lr upper and appropriate muzzle device or the direct thread/taper mount. 
With what comes in the box the only wat to use with .22lr is with the pistol booster. 

With all that said, I can't see it being that much of a difference. I've never tried because I have a Checkmate that I use with all my rimfires. 

Thanks for the response.

Items I ordered already...
Direct thread adapter for .22
Taper mount break for ar15
Minimulast blast shield
Cleaning brushes

Now I need to go try it!

That blast shield is handy even when not suppressed. It does a great job keeping the concussion "down"

Please correct me if I am wrong, but if using a 3-lug mount it will limit the Optimus to the short configuration? And, isn't that going to be hard on the baffles when firing a 5.56 (in my case a 10.3 bbl)? 

Prib 

Yes, with the 3-lug mount it can only be used in the short configuration which is rated for 14.5" barrels in 5.56.
For that length barrel you would want to throw in the blast baffle and put it in the mid length or long configuration.