Finally ready to mount a light and sling on my 590 Mariner...suggestions needed

[AcceptableUserName]

Bear with me, this will be a bit lengthy because these components need to all work well with each other. I have a 20" 590 Mariner. I'm ready to mount a light on it.

The light and light mount need to work well with the Heatshield and heat shield spacer. I'm going with a Streamlight TLR-1. The spacer on the Mossberg heatshield butts all the way forward against the front barrel lug. For the tube clamp rail mount, I'm going with either this

http://www.cheaperthandirt.com/SCP837-1.html

or this

http://www.cdmgear.com/mtdetails.html

or this

http://www.opticsplanet.net/streamlight-12ga-extended-mag-tube-tactical-mount-69901.html


Doing this, if I want close control of the light I WILL need to modify the spacer, so it butts up directly against the clamp. If I opt to mount the light way up by the muzzle, the heatshield will depend on the clamp less, but the light will be out of reach without taking my hand off the forend. What do you think? Do you foresee any problems with this? As always, I set my guns up with all business in mind...if it comes down to it it WILL be used and used good so I want to know everything will hold up shipshape and do things right the first time to ensure that. What do you think of the spacer shortening modification so it can butt up against the clamp? Doing this, I'll need to make certain the clamp I choose WILL NOT move. Has anyone here shot extensively with the Laserlyte clamp in place? Did it move? I know the CDM clamp has a reputation for NOT moving.