Flow predictions are a risky business. I heard somewhere that this hydrological year will likely analog somewhere between years 2002 and 2007 (may not specifically apply to the Yampa drainage) but that's what it looks like right now which would put June 22 closer to 1000 csf if that.
Our group put on last year in early June with the flow right at 1000 csf and dropping fast. Most of us opted for packing light in small craft--small cats, small rafts, duckys, tandem canoe but the folks in a 15 ft raft with gear did fine. Warm Springs was pretty tight and who knows what the new Warm Spring will look like.
Biggest issue was lots of flatwater and slow current. Defintely request the extra day and be there ready to go morning of your put -in