IMHO, I wouldn’t set the target to -60 anymore.
For my 2c,-- the chain signals will be worse on a 3000 vs a 1000 if the overall target is -60 on both. I’m not complaining about the 3000’s at all – its just the way 4x4 works.
The reason is: A -60 target on a 2x2 system will be ideally comprised of a -63 + -63, which add up to -60. On a 4x4 system, if you have the target set to -60, it will (if things are perfectly balanced) be made up of -66 + -66 + -66 + -66 (which add up to a -60). So setting the target the same, will result in LOWER UPLINK powers.
Plus - of course - on a 2x2 ePMP1000/2000, that -60 might not really be a -63 + -63… maybe the chains will be a -62 & -66, but the point remains… in a 4x4 system, that -60 target 'might theoretically; be made up of -66 -66 -66 -66 (adding up to -60), but the chains will probably be something like -66 -71 -65 -73, and still add up to -60. On average, the chains will be -3 db lower if you use the same target.
SO - on a 2x2 system, the chains will need to be 3dB stronger in order to add up to the -60, and the AP will tell the SM’s to turn them up by that 3dB. On a 4x4 system, each chain will be turned down 3dB weaker, in order to add up to that same -60. SO - DON’T USE -60 AS YOUR TARGET.
SO SO - for us, we have our target on 1000/2000’s set to -59, and on 3000’s we set it to -56 – and that get’s each chain of each SM associated at the same signal strength.
Now - you may be having other issues for other reasons of course, but for starters - if you only set your overall ‘target’ at -60, then a 4x4 3000AP will tell it’s SM’s to turn themselves down 3dB quieter than a 2x2 1000/2000 will - and that won’t help your situation. IMHO, I’d try -55 and see what results that gives as a starting point, and work from there.