The official groomed trail stops in Chassell. Options if you are dead set against riding Portage Lake:
1) Ditch bang / scrap roads from Chassell to Painesdale. Once you get "on top of the hill" a mile or so west of Chassell there are a lot of rideable ditches (or what look to be rideable from the road). But there is still going to be some road scraping and you have to be comfortable ditch banging and dealing with 2-3 foot snow banks in a couple spots.
2) Ride the old RR grade (now bike path) from Chassell to Houghton. About 10 miles on a 5-6 foot wide ungroomed path (1+ foot tall moguls at this point) going over hundreds of driveways.
While it seems like the OP is pretty dead set against riding the lake, I will reiterate my experiences with it (and the general Baraga area) from 3 weeks ago. We took 109 south from Twin Lakes throught Alston to 15 north to Baraga and Chassell. The trail from Baraga to Chassell is actually a really nice one once you get 5 miles north of Baraga - definitely see some different type of scenery. Once in Chassell we took the lake from Centennial Park north to Ripley, and ended up being the nicest 10 miles of the day (and there were plenty of other "good" stretches that day). Prior to us being on the lake, there had been a strtetch of 36 hours above freezing, including topping out at 43 degrees the day before. We encountered no slush pockets despite the warm weather, everything was firm and solid.
For anyone looking to go from Baraga to Houghton and are debating 15N versus trail 109, know that the Baraga grooming on their northern portion of109 has been questionable at times this season. There was a distinct lack of snow on it around Alston three weeks ago, and I've heard from a couple different sources that Baraga sometimes doesn't groom the final stretch north of Alston (which is narrow woods riding to begin with). They also updated their MSA page today saying they were only able to groom to the Sturgeon River due to the hills of FR2270 being slippery, meaning a good 20 miles between there and where the Superior club picks up hasn't been groomed.
