I'm thinking that my Pugsley was offset 17.5mm, but again, this was to allow for clearance in all gears. With an Alfine out back, and a single ring up front I reckon it's do-able, and should mean a non dished rear wheel. So even though the hub stance is narrower, the lack of dish should keep it plenty strong. Certainly more so than my old offset pugsley rear, which never gave me trouble anyway.
I'm thinking that my Pugsley was offset 17.5mm, but again, this was to allow for clearance in all gears. With an Alfine out back, and a single ring up front I reckon it's do-able, and should mean a non dished rear wheel. So even though the hub stance is narrower, the lack of dish should keep it plenty strong. Certainly more so than my old offset pugsley rear, which never gave me trouble anyway.