Rd dot doesn't line up with fts magnifier
 

So my red dot sight sits at 3 cm to centerline from my rail and my fts magnifier sits at 4 cm to centerline from my rail. Ideas?

You can use a riser but the lowest one I think is .5" which is about 1.27 cm. :)

http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40

What kind of red dot and FTS magnifier. eotechs and the eotech style FTS should line up no problem. Some Eo's may need a EOtech riser.

Chances are you have a Aimpoint FTS magnifier. So like already mentioned a riser for your Eo-Tech or sell the FTS and get one meant for a Eo.

It's a EOTech L-3 magnifier but just a aimpoint red dot. I'm wondering if a red dot with a quick detach mount would work.... no one seems to provide specs on heights in the ad descriptions

Aimpoint and Eo-Tech FTS Magnifiers are spec'd for their respective sights. Your best bet would be trading someone for a Aimpoint FTS, or get yourself a Eo-Tech reddot to go with the Eo-Tech FTS.

Yeah, you don't use a T-1 mount for an EOTech holo sight, so why would you use an EOTech magnifier for an Aimpoint sight (bad comparison, I know, but you get the point)? Its meant to be used strictly with EOTech 55X series sights.

What model of aimpoint and what mount are you running? A low mount vs standard 1/3 mount will give you a different heights. You may be able to use the eotech riser on your aimpoint (depending on model) to get it to the correct height with your FTS.

option B as discussed trade the eotech 3x for a aimpoint 3x.