I moved the rear chamber panel back a bit to fit the pd1852 in, to keep the horn flare rate the same I adjusted both the main horn angles by 5mm, and shortened one panel by a few mill, there was no difference in sound or Rta response when a/b with the original design both loaded with the pd 1850. The pd1852 plays lower and and sounds a bit more aggressive in them. The changes made were very small, but helps with the driver not hitting or touching the back baffle.