I agree Wolf, backing is a good Idea and I use it. My point was that even on those few occasions where I have not, the 4000 has stood up to the line stretch pressure and I have never had one fail though I understand it has happened. It is amazing how much pressure mono can exert. Try wrapping a few loops around a finger and you will get the idea when it starts to turn purple.
Recently I bought a Daiwa M1 and I am not a fan. After just a few days fishing, the drag tends to creep out on the downrigger unless you have it cranked down way to tight. Perhaps I just got a bad one but I am not about to buy another one to find out. That said, I just bought my first Islander MR2 and I am curious to see if it’s worth the substantial additional cost compared to the Shimano.
Speaking of the good old days, an old guy I fish with (his boat) still uses a Peetz rod and wood reel with the 2 lb ball suspended from a hanger. My side of the boat has the downrigger but there is the occasional day when the salmon seem to prefer the old Peetz set up. I have got to say you get a work out bringing that 2 lb ball up to check the bait. I have tried to convince him to put some backing on the Peetz but he insists on sticking to a piece of carpet he has taped to the reel under the mono. Old habits die hard. I understand the old Peetz wood reels were really designed for wire line not mono, - no stretch, therefore no excess pressure on the wood.
I have thought it could be interesting to have an Old School Derby one day. Only old wood Peetz reels and rods with old metal flashers or dodgers allowed, - no downriggers. I am going with a Pal #4 dodger.