I have primarily two kits, and two sets of plates, Hesco 4401 medium shooter cut (7.6lbs) and RMA 1092 (4.5 lbs).  One for myself and one for the wife.  I was thinking of putting the Level 4 4401 in front of each PC and the RMA 1092 in the back, this would distribute the weight between each carrier and also provide adequate LVL4 protection in the front.  

Are there folks who do this, or is it generally frowned upon?  The main benefits I see is better weight distribution (each PC would only be 12.1lbs in main plates) and each gaining LVL4 protection in the front.  Downside is obviously 12.1 lbs is still 3 lbs heavier than a PC solely using the 1092s, but then that PC loses lvl4 protection.  The two PCs in discussion are the LBT QRCv2 and an Agilite K19, the LBT does have side plates while the K19 does not.

Have you tried it out to test the weight balance?

One thing to think about is weight distribution on each carrier (not just between them). Do you have mag pouches on the front? Any other gear strapped to the back? I’d try it out around the house to see if the weigh differential front to back causes either one to be uncomfortable.

You're right, did not consider front to back weight distribution.  I am still waiting for the Hescos to arrive so I have not larped in that configuration yet.

Yes, each PC has front mag pouches so when you consider the 3lb extra weight on the front in addition to the mags it may be too much.

I did this and didn’t notice any weight distribution issues. I have not walked/jogged with it yet. Just around the house.

If you are into mixing plates, the optimal mix is plate shape...

Your back plate can be more square while you front needs to have cuts for your arms to move.

I wouldn't worry much of the difference in protection levels. All that weight for 1 round of AP is a heavy price unless you're fighting americans in ww2.

This is absolutely pointless and will only serve to make your front plate bag sag like crazy, especially once you load up your front with mags and other stuff.

I doubt you will face an AP threat CONUS. Lvl 3+ is pretty much all you need. Put the 3+ plates in your primary carrier and use the lvl 4 bricks for backup or whatever.

This. I've been experimenting w/2 single-curve plates (III+), multicurve front (IV) & single-curve back (III+) and multicurve front (IV) and back (III+).
IMHO multicurve front is a must and multicurve back highly desirable. Difference in comfort while wearing is significant.

Tomac

Ideally, you would end up with a more square plate on your back and a more swimmer cut in front....imo.