Make sure that the caliper is perfectly square to the rotor. Make sure that the pads do not have taper. Make sure that the rotor run out is within spec. If these are all correct, they generally will not squel. Mine sure don't, ever. We are talking about less than .003". .000" is best but unlikely. I have used Wilwood T, D and J(BIG dust) compounds all with out a hint of squel. I also sounds as though you may be getting out of the temperature range that your front pads where designed for. Do you notice any signs of fade? Think about when they are squeling and you will know why I ask!
If you can not get the front and rear to lock by adjusting the balance bar, then most likely your inherent balance is off or the balance bar is binding or you have a failure some where. A pressure gauge is a big help here. Balance is affected by pads cf, rotor size, pistons sizes (caliper and master cylinders) and even tires and compounds.
I use EBC pads on my girling calipers in the rear. Really like them.
Last but not least, Bob is the expert here!
Rick