Lance,
You've chosen a fantastic route, my friend! Just make sure you drive thru the long tunnel southeast of Zion. It's really awesome.
As to your GPS question, I've had the same problems as you've had. Some of it I think may be traced to the settings you have (by default or by choice) on the GPS in your Boom!Box. But there may be settings on the web page you haven't found or explored yet either.
When I tried it with several routes, I gave up. I did get it imported into my Boom!Box just fine, but that's when the problems began, and even though I'd seen the route I wanted on-line, that's not the route that my GPS chose for me. I'm thinking it may have been my internal setup doing that to me. I finally turned it off.
But...I'll keep trying. This new GPS is a real turd nugget compared to the older Garmin's I've worked with, and I've had several. Go back and read your bike's manual for the GPS. Study the map maker a little more on line and read/watch the tutorials more closely.
Then when you have it all figured out, let the rest of us with less patience know how the darn thing works!

Just kidding, Lance, and I know you know that. I'll be spending a little more time with it this weekend on-line and with the bike. I want to plug in a route to Memphis for us, so I want to learn what I can about it. Maybe I'll have words of wisdom to offer soon. (But what would be the odds of that?

)