Epic Blarney Loop is a fun challenge that the canyoneering community thought up to turn what would normally be two separate downhill canyon runs into a pretty Rad loop.
Road Trip Ryan claims West Blarney is the best canyon of the North Wash.
As for the speed-inclined-canyon adventurer...
All out. In sand. 4th and 5th class obstacles on the way up East Blarney. Crazy chimneys and one biiiig drop (5.8ish chimney, 15 meters) that you will want a rap or handline for on West Blarney. (Note: I regularly free solo 5.6-5.7 multipitch and I brought a handline, sandy chimneys...seems wise to back it up) Do your research and rehearse the route for a lap or two before trying with the gas pedal down.
If you do this it will be the most fun 5k-10k equivalent effort you do all year.
I think sub 35 is low hanging fruit
Sub-30 is pretty epic status.
And will someone who knows this by heart and has great legspeed go sub-25? Quite possibly
I think approaching 23min is magic, Unicorn ? shit.