i recently purchased a DPMS m4 style carbine (.223 cal) and a harris bipod with the #5 adapter. my problem is that the DPMS handguard has ribs inside of it instead of the aluminum heat shield. the ribs make it impossible to fit the adapter needed to mount the bipod inside the handguard. do any of you know how to make this bipod work? do i need a different adapter or should i just modify the handguard? thanks for your help.