I also use fortec 1.8m prime focus dish and BSC621-2 LNB, and I'm in greater Seattle area.
I locked 3900 V (ETTVs and AJE) fine, quality 65-67% on CS 4K, and video/audio are fine.
I have problem with 3780V, I lock this tp fine, Q:65-67%, but videos and audios are garbled.