I used H1's. Fairly easy IMO. The vast majority of the time is spent cutting the shrouds so they actually fit inside the housing.
Someone has done FX-R's. However, they had to cut the top and bottom of the housing and fiberglass around the projector for it to fit. Too much effort IMO, even though the FX-R's have a MUCH better output. Just not worth the effort involved for me to do it, especially since I don't DD my prix anymore. The Mini's provide enough light since I'll rarely drive the car at night. Actually thought of going back to stockers since i'm not a big fan of the way the retro's look on these.