Somebody stop me?

Wish I knew, but I don't... I will give your method a shot though--it looks promising!

Bounce down the clip before you decide, the online algorithm is much worse than the offline one.

I have made 100's of songs and most of them start with me on acoustic guitar playing to a drum pattern. I dumped all the patterns from my trusty old Roland 505 to midi 20 years ago and I still use those almost daily. 
It's a myth that a song won't sound "human" if it's locked to a continuous tempo. baloney,  All that "humanizing" and what not just make things worse.  Do not fear a steady groove. Its all good stuff. I've played in bands that are tempo solid. We would be recording 4 minute songs and each take would end in almost the exact same spot. 
You humanize it by adding real instruments which will all be just a little off the beat but hopefully in a musical way. Drums.Bass and keyboards should be locked in tight,, lead guitars and vocals are allowed to be loose gooses.  

For a 100% accurate tempo map, I personally go the manual mapping way of turning on the click, opening the tempo view and hand drawing the tempos while the music plays. If the click starts to rush or drag, simply draw in the appropriate tempo change in the spot where it rushes or drags. When I'm done it's clicking perfectly in sync and I know the map is precisely the way it should be. After that for me it's slip editing the beginning to zero and bouncing the clip into place. Then I highlight the clip and open the audio snap pallete view, click Clip follows project (auto strech). Now at this point the tempos can be redrawn to desired tempos (or delete all tempos but one in the tempo list, you can change it there too). NOTE this is Online rendering in Groove-clip mode and once the desired tempo/tempos are acheived will sound MUCH better when bounced down using radius Mix. Don't give up hope! Any way I can help let me know! You can dropbox me! I did finally get around to trying melodynes tempo extraction and for a conducted orchestra peice with a full band and it couldn't stay on beat to save it's life. I've been hand mapping for years and find it relaxing and reliable! March to the beat of your own tempo map!

There is a better way so long as you kept your tempo within tolerance and didn't drift too wildly. I haven't actually tried this yet, but I heard that you can drag and drop your audio clip on to the time ruler and that will make Sonar's tempo follow yours. I.e any tempo changes/drifting you did, will be sorted by Sonar automatically. Then add Addictive Drums or such like and it will stay in time with you! As I say, if you drift off too much it will be noticeable as everything will slow down/speed up together, but then you can also use that for say, an outro slowdown or any other intended tempo change.
 
And talking of click tracks, guide drum patterns and drummers keeping tempo, I have almost always given drummers a click track to follow, even back in the days of tape when I started out. This is because they are coming into the studio to produce a refined, polished version of a song, often to go on an album. Unless you are going for a live take, always use a click. Not only does it ensure a consistent tempo throughout the song, but it also lines up the DAW with the song making it easy to work with, edit, sync to and for the other musicians to stay in time with. The best drummers are those who follow the click precisely but drift in and out ever so slightly while still staying bang on if you know what I mean. 

Ever create a thread and then wish ya hadn't?
 
Hosts, please delete this dog of a thread.
 
Thanks to all regarding groove clips n' such. :-)