Just a heads up. Tunnel is rocking a sweet detour right now up tunnel if you hit it during the day. It's 100x better than the old detour. The one today takes you up Hiller..... good god. My Garmin was seeing 24% grade, a new personal high. They have a shuttle that takes you to the top if you need to.
I've only done Hiller once, probably the reverse way to the detour you're describing - it's pretty steep either way, but descending that long slope was insane and not pleasant. I vaguely recall a red blur where I thought there might have been a stop sign at the bottom.
Edit: here's one I made earlier - going the opposite way, I think