If you land, on-time, at 4:25, you should be deplaning by 4:40ish...depending on which area you land in (I've landed on a runway so far from the terminals I thought we had landed at Sanford!!). To the tram, down to level 1 and DME around 4:50ish. Wait for the bus, 1-25 mins, on the bus, waiting to leave the airport, 1-20 mins, drive to resorts, 30-45 mins. Get to room, drop off carry-on bags, freshen up (because even if you say you won't, everyone has to check out the room!!), walk to the dock area, 5-10 mins (depending on where the room is), wait for the boat, 1-20 mins, boat to DS, 25 mins, walk over to Paddlefish, 15 mins. We always recommend figuring on 90 mins, from gate to resort...so, that's going to have you arriving at POR around 6:15ish. I would add on at least an hour to get to your room, then go to the dock, and get to DS.
Sure, you could do it in less time if the stars align, but it could also take you a bit more time as well. So, I would say you can make it, but don't dilly dally!!!