Thread: Route Calculation - seems odd

Hi, i'm a total new user, just purchased a pre-owned 2012 Kia Carnival - and its onboard Nav was years out of date - So I've installed iGo Primo 9.6.13.405512 with HERE 2020H2 maps for Australia onto SD card and gave it a try
and after much reading of various threads on here , I've sorted many of my initial issues.. but one thing remains...

The route it chose to send me on, during a weekend trip from Werribee to Warnambool a trip of ~ 3hours and 230KM's. Regardless of whether i chose Fast,Easy,Short or Green , it would persist in wanting to leverage B & C roads... now our local C roads may well be sealed, but they are narrow, and poorly maintained, so we would have preferred to have stuck to the Motorway & Highways.

Here is a table of the Route it chose , along with alternate routes.. the final line is after i manually entered a handful of waypoints to FORCE it to stay on Highways.

Spoiler: Route Table

[Only registered and activated users can see links. ]

I have subsequently discovered i can 'trick' the Nav to use my 'preferred' route , without me adding waypoints, if i set my profile to 'Truck', rather than 'Car', however - if i change the Truck profile maximum speed from 80KM/hr to 100KM/hr it again goes back to choosing B&C road routes. I've seen in one of the stickies relating to sys.txt , there is an [defaults] entry known as mainroadness=60 .. I've tried differing values for that setting - but it didn't have an obvious effect.

Does anyone have some suggestions on how to better favor using main highways and roads , over B & C roads ?