If you run a stock, and especially if it's one like the second picture, then run your red dot sight on a high rise grip mount or similar. You'll need the clearance since "we" wear masks that get in the way while "they"(soldiers) don't wear masks so they can tuck their faces down onto the stock and line their eyes up with the sight.
I know it doesn't look very "mil sim'y" but running just a regular bottom line and mount a red dot to the top weaver rail is one great way to go. It fits in with our need to wear the protective mask.
And woodsball isn't as much about looking like a regular soldier by dressing up your marker as it is about just staying hidden and hopefully making that first shot count. So dull black or dark dull green for the marker is good. And a red dot can help you put the first ball's likely landing spot where the guy you're shooting at is.
I like my red dot sigths. And I like my black markers for staying hidden. I've played woodsball with an electric blue autococker and one of the other guys said I stood out like I was running around with a big neon sign in my hands
I'll still play with my blue neon but I know I'm at a disadvantage.
If you do mod your MR like the first one I'd suggest not using the front grip and to mount the red dot back by the hopper. I'd also suggest one of the 1x30 tubular red dot sights. I've got a couple of the ones like in the picture and one of the 1x30's. the 1x30 is far more clear and nice to see through and is much better protected for when it gets hit.