@modaniel
We are talking Union Canal - goes from Lochrin Basin to Falkirk where it meets the Forth and Clyde Canal (via a large wheel or lift). You come off it just before the hamlet of Hermiston then cycle through that hamlet to Heriot Watt. It is slightly sheltered from the wind except on the Slateford Aqueduct where signs tell you to dismount and push.
the rush hour on the union canal towpath is 8-9. The traffic is all heading into town from the aqueduct east. If you joined the canal after the aqueduct at the lanark road you would not encounter traffic. If the towpath was wider you would be going against the flow but this is not really helpful as the path is not two lanes.
THere are various lecturers and students at Heriot Watt I recognise from my commute into town as they are coming out. As the route is entirely flat you will never have the issue of cycling uphill into the wind. I would go with 12mph as a speed once you are beyond the aqueduct. If you stay in Colinton then it would be 30 minutes, if you stay in Polwarth then it would be more like 45 minuites as you would have the aqueduct and some traffic.