I bought the DM 3575 from Phil at SFI also, several years ago. Cuts 6'. Retired and downsized my operation and sold my JD 1209 swather. I mow with my Branson @ 57 PTO hp and that's more than adequate.
I tried using sickle bar mowers numerous times over the years and in short, they just don't work for me; Period. Looking for something that did work, I looked into disc mowers. Too many moving parts for me and every used one I saw had braze repairs on the bottom where the main casting had cracked. On buying new, this drum cost half as much and guessing has less than 1/4 the parts to break/wear out.
I liked the idea of the drum and watched his videos on the www.
Pros and cons from my experiences:
Blades are 25 cents apiece and the OEM uses 6 which are reversible. I find that after mowing my 7 acres I have to change/rotate at least one (getting dull, nicked). Only takes a minute to change out; nothing like a sickle bar or section.
Blades do get gummed up with mud and grass, for me anyway, so after a cut I will clean them out so that the blades can swivel freely. Cutting coastal on a dry field probably wouldn't be a problem. It still cuts ok but I want the blades movable so that centrifugal force can throw them out into the cutting path like they are designed to do. Takes all of 15 minutes.
Like any rotating side cutter rocks can be a problem. There is a curtain around the drums but it usually is deflected to the rear and for me was of little help. I was cutting a neighbor's place and I suppose I hit a rock because all of a sudden the door of my cab shattered. I understand some folks with side cutters have installed a plexiglas shield on the right fender to prevent such occurrences. Rocks were visible on the ground. Course if you have none then there is no reason for concern, like on my home place.
I had Phil install the 1" extension to increase the cutter height to a stated 3" off the ground for better stubble retention and faster regrowth with the Haygrazer Suday-Sorghum Hybrid (stemmy) I usually plant. As it turns out, the mower bends the stem over slightly and the stubble actually comes out at about 4 1/2 inches long which is even better.
Initially I had a problem with the belt shield and the way it was adjusted it came in contact with the belts and damaged them (4). I sent Phil pictures and an explanation in my opinion as to what had happened so that he could correct it for future customers. I had a full set of belts within a couple of days, no charge.
At 900# (for my 6') and riding at the side, in the mow position, but 3 pt. raised, it can be a problem for the left front tire coming off the ground. Since it rides on the ground, once you drop the 3 pt to the mow position, there is very little weight on the tractor. Phil knows this and knows how to determine if you have enough front end weight to support the mower in which you may be interested. My tractor is 4wd with a FEL (fast attach bucket removed for mowing) and is more than adequate.
In moving the mower from the transport position (straight out the rear) to the cut position alongside the tractor, a little common sense goes a long way especially on the 6'. By setting the mower on the ground like it is when cutting, you can use your tractor to back into it or move away from it to swing it from one position to another which doesn't require any manual dexterity. The PTO shaft does have to be removed (at least one end) to allow the mower to swing from one position to the other and may be a minor inconvenience for those moving from field to field. I can move mine in the mow position and once I hook everything up initially, I'm good to go.
Unlike a swather, there is no crimping function with a pure disc or drum. Since I plant stemy crops I bought a crimper to smash the stems and provide for faster curing. On something like Bermuda or Rye, crimping is not necessary. Yes this requires a second pass across the field but you have that with any non-crimping mower, sickle, disc, or drum.
The mower has the ability to follow a sizeable slope. I have a 1/3 sloping bank on my pond/pool/tank and this mower easily conforms to the slope and does an excellent job of mowing such. Phil shows some of that in his www videos.
In short I am happy. Great product, great service and a great price.
Hope this helps someone.
Mark