Carry with Internal Frame Backpack

Summer is again upon us, and I'll be heading to the mountains with my kids. Does anyone have suggestions for carrying a pistol with a large internal-frame backpack? I'd like to carry my pistol in a robust, secure way while hiking, with it quickly accessible if needed. Here's some of the issues I hit last summer:

• IWB or OWB (reg side holster carry): Internal frame packs have large belts, so carrying IWB or OWB is out. The belt takes most of the weight and needs to be tight against my body. Smashing the gun between the pack belt and my body is not a good thing.[/*]
• Shoulder Carry: The shoulder straps of the backpack get in the way. Same problems as OWB.[/*]
• Pack Belt Carry: I've tried strapping the holster to the thick, padded pack belt itself. This actually held it very securely last summer, but the gun hits the dirt every time I drop the pack. It got the gun really dirty and I started moving it to a different location when we'd stop so it stayed clean. It's a pain (and not really safe) to move the gun every time we take a break so I can take the pack off and put it on the ground.[/*]

Any bright ideas? Or even just ideas?