Just a thought .... I worked with many PLL eval board from different mfg. and I found it very cumbersome to remove small smd components from the main board to populate a new PLL filter loop. How about a modular loop filter system. ...instead of removing component from the main board how about using some sort of micro socket and external mini board ...the user would just plug its own custom PLL loop filter circuit board into the main board ???? I think it can be better to work on a separate board than risking to damage the sensitive product from many soldering and desoldering steps. (sorry I'm french so my english is not perfect) .