"Stacking" lifts?

That's what i'm doing. I have Icon coilovers with 1/2 top plate. But i'm not 4x4, You'll also need to make sure you don't over extend your CV axles.

 

1/2" plates won't cause any harm, using 2"+ top plates with 5100's just seems like a waste. If you want to use top plates that tall, don't bother with getting a ride height adjustable shock, you're paying extra money for a function you aren't going to use. That's why I said there's no good reason to use a spacer lift with 5100's.

5100's will get you to 2.5" of lift +/-. You can then use the short top plates to get you the rest of the way to 3".

 

Get shorter rear blocks to lower the rear a little instead, it will be less risky than putting spacers on 5100s (which is a bad idea), and it will be cheaper too, you wont have to get new UCAs. Just tell people it has a 3" lift, and dont mention that it is really a 2.5" or 2.75" lift, no one will know the difference.