I have a 2018 Vegas 25.5.
I have done it both ways. It is impossible to add oil through the front without getting oil all over the engine and the driveway. Maybe someone with longer arms could do it but I couldn't hold the end of the tube in the engine spout and the other end of the funnel up in the air and the oil container up in the air and pour the oil with my 3rd arm.
I use the through the top of the dash method: much easier once you make the original alterations to the dash under the desk.
Alajeu
__________________
|