It's hard to tell if this is a terminology concern or not, but "root" nodes do NOT have params - only View nodes do. If you do not have params.MyCustParam, then none of this is going to work.
Please provide the code as you have it currently, as well as a screenshot of the params of the View in question.
I just attempted this myself in 8.1.12rc1 and it works exactly like I would expect, so there is either a configuration issue with the View in use, or your code. If you could supply the view.json file of the View you are attempting to navigate to I could examine it and provide the exact code you need to use.