Has anyone ever used any of the fold down sights on a side fore-end rail?  I'm looking at this option on my AR build, as it will be a dedicated coyote rifle.  My reasoning behind this train of thought is to provide both a scope (for long range shooting) and open sights (for short range running shots).  This would allow me to simply rotate the rifle to have the use of the open sights when the situation arises.  If you've ever tried keeping a yote in your scope when inside 100yds running full bore on a crossing pattern, you'll know what I'm getting at.  

Unfortunately, with this being my first AR build I'm not familiar with the various folding sights available, and if they would work in a situation such as this.  Would the mounting height being the same cause problems, and would I run into problems with them being so close together (and the rear so far from my eye)?

side mounted irons, think closer.  like 30 yds.

if your closest shot is 100 i would go 3-9 at 40mm.  

JP makes something that might accomplish what you're describing. I haven't tried them, but noticed them while on the JP website.

Check it out:

www.jprifles.com/DetachableSights.shtml