OK, can you reproduce this with IPlugBetterGUIResizing? For me it is working properly here... Did you put this code in your project?
Code:
enum EParams
{
// This is reserved for GUI resize
viewMode = 0,
windowWidth = 1,
windowHeight = 2,
// -------------------------------
// Your custom parameters:
kGain = 3,
kGain1 = 4,
kNumParams
};