I've had a problem with the regulators fighting with each other. I match their voltages closely via the trimpot, switch both on and they sit there powering up and instantly resetting. I know having two regulators connected together can fight when their voltages are different but I don't quite understand when the voltage is within 0.01v or so.
I believe that putting two (or more) voltage regulators in parallel with closely matched voltages is the worst thing you can do. Power supplies have the opposite connection rule from loads: voltage regulated supplies go in series, current regulated supplies go in parallel.
If you want to put voltage regulated supplies in parallel, this is what you do. Set all but one of the supplies to a higher voltage than the load needs, say 6 or 7 V. Then set the last supply to the regulated voltage, e.g. 5 V. Then this is what happens: the 6 V supply will deliver as much current as it can in an attempt to reach 6 V. Of course it won't reach 6 V because the load is too heavy for the supply, so it will become current limited. Now the second supply, the 5 V regulated one, will deliver additional current until the load voltage gets up to 5 V. Once this happens the supply will start regulating and keep the voltage at 5 V. So one supply will be in a current limited state delivering maximum current and the other will be in voltage regulation.
If you set both supplies to 5 V, then they will be unable to decide which one is taking the constant current role and which one is doing the voltage regulation and they will fight and go unstable.
If you need current balancing between the supplies then you need to put a balancing resistor on the output of each of them to separate the voltage regulators.