Is there an option within iGo/Primo, etc, for calculating a route based on a max speed?

When I tow my travel trailer, I limit myself to 55mph for safety and mileage reasons. I'm sure that Primo will plan a route based on higher speed limits whenever possible. I'm also sure that there are instances where it will avoid roads that have a 50 or 55mph max speed rating in favor of 70mph Interstates. If I'm not doing 70, this might actually cost me time. Would it be as simple as asking for "Shortest" routing as opposed to "Fastest"? I haven't actually tried it, but I'm guessing that this method would take me through town centers and on really minor secondary roads. Thoughts?

Go to vehicle profile and set your vehicle's maximum speed accordingly (primo only).