why do you want to smoke it at such a high temp?
I wish I could help, but I don't go by time anymore, only meat temp and "looks".
Best thing I bought was a remote thermometer. I want a couple more just in case mine go bad, and one is I believe. (about 20* cooler than actual temp)
You really gotta go by meat temp, I 'm sure you know that. As far as time..........well allow at least 1hr/# give or take 1/2hr.
Lotta help huh? Sorry, wish I could help.
Keep your head up, grab a Mt.Dew and some "hard stuff" and that will perk you right up.