I've had a lot of issues with the feed rollers on my 439 - gumming up and imprinting whatever is stuck on them onto the stock - if it's softwood (but not so bad with hardwoods). The end of session routine now includes a severe wire brushing, with heavy gloves on in case.
On the DX, I still have the oval port. It was a right PITA until I noticed there was a four inch nail welded vertically across the middle of the port - long shavings wold wrap round it. It was painted green-ish so I don't know if it was an original fitment or not.
Anyway, getting rid of that and the grid on my DX's inlet seemed to fix the clogging issues, mostly, but I try to have as few bends and kinks in the port as possible. I support it from the roof of the shop, which is quite low, so it comes out fairly horizontally, and only turns up into the DX (inlet port points downwards) at the last minute, in a slow bend.
I have to say it surprised me when I got it: It's quite low tech and like the 419 tablesaw, I was unimpressed by the engineering (I stripped it and thoroughly cleaned and fettled it). But it performs quite well (I do get thicknesser snipe, which I put down to technique mostly - I can avoid it). I know the lifting table sort are slow to switch over (the 439 is pretty quick), but they have the big advantage that you can thoroughly clean everything. Getting at those rollers - awkward!
I did one useful mod, fitting a 16A inlet instead of the mains cable. It is much happier on the 16A circuit than domestic mains, and there's no trailing lead when you move it about. The plug fitting is bolted to the side of the blocky motor cover, where it's well out of the way.
I've also replaced the square blade clamping bolts with hex headed ones (same grade of steel and length - very important). They are easier to spanner, I have spares, and overall nicer. Two things are very important though: you need to slightly dome the heads and get rid of any raised lettering, AND they all need to weigh the same (as close as you can measure them), so the block stays balanced. I spun mine in a drill press (I have no lathe), against a file and wet+dry. I did enquire about the original bolts (a previous owner mangled them), but they were some silly price.
Finally, the thicknesser table's chain drive was seriously blocked with shavings when I got the machine. You can't clean there unless you take it off the legs and tip it over. So I've blocked the holes in the corners of the thicknesser opening (and two more in the middle under the table), to minimise how much sawdust gets down there. So far, the rise and fall has been great. Don't forget: if you take off the chain that the four sprockets are indexed - mark them with tippex or paint or tape, so they go back exactly the same - otherwise the table won't be parallel to the cutter block, or worse, twisted diagonally!
I made a trolley for it a few weeks ago, which makes moving it around much easier. It's also a better height - I find the thicknesser particularly is too low for my back! But overall I am fond of it - small but very useful.
To the OP: I use roller stands outboard of the thicknesser, for long stock They are a pain to set up but they work well once they are at the right height - use a long straightedge to get them spot on and level. I have some non-castoring wheels left over from the trolley project, so I'm thinking about using those instead of the wide rollers (two sets of four - I binged on Lidl castor sets!).
E.
PS: for cleaning it would be really helpful to be able to use the cutter block to inch the feed rollers (no power anywhere near, obviously!). IIRC, the morticer attachment is a 10mm left-hand thread (or similar), so hard to find, but a suitable fullnut and MIG welding a bent bar onto it would make a tool to do this. Then all you need is a small LED light and a bit of mirror as wide as the thicknesser platen to see what you're doing more easily...