Attaching a laser to a 4ft level for fence bulding

[Butch777]

I'm looking to strap a laser to the top of my level, to help set up a iron fence.
It runs over uneven/hilly ground, for about 65 feet.
It looks like green is the best color for outdoors.
My question is trying to keep the dot as small as possible at 65 feet.
I'm looking at 20mw to 100mw in power.
If I go with a higher mw, will the divergence be less??
And also will the dot be more visible with a higher mw??
I'm also guessing that it should be focusable and maybe a glass lense.
Any help would be appreciated. Butch

 

[Anthony P]

I have installed many fences professionally as a Lowes contractor. The individual posts need to be plumb. The top will follow the contour of ground to some extent. Is your iron fence in sections? Chain link?
Rather than trying to build a laser tool, I would suggest renting a transit. Even with a transit, the optical telescope type are easier to use and more accurate than the laser type.
If you have some photos of what you are doing I will try to help...if I can.