To prevent a signal boost when partially panned and using a pan law between -3 dB and +0 dB, choose "linear taper" or "hybrid taper" from the pan law dialog.
Here is the output of a panned sweep for sine, linear, and hybrid taper with a pan law somewhere around -1.5 dB, because that is a useful level for this visualization. With +0 dB pan law, the linear and hybrid tapers are identical.