I just picked up and assembled a Supermax 19-38 and ran a few test boards (pine and maple) through it. This sander comes with 80 grit installed, which, as expected, leaves some pretty deep scratches in both wood types.

I picked up some 120 grit also.

I plan to use the sander for final dimensioning on some soft maple stiles and rails for flat-panel shaker style doors. I'm thinking multiple passes with the 120 grit is the way to go. I don't have very much material to remove, just remove a few marks and small ridges from jointing/planing. I probably should have picked up some 100 grit, I didn't expect the 80 grit to be quite so scratchy, it is very different from a ROS.

Also, do people run stiles/rails through 'on-edge' to thickness the width of the boards (i.e. the ~2" width)? I'm thinking I should pass a half dozen boards at a time, side-by-side, together, grouping ones of a similar length in each pass. Is this a common practice?

I also planned to use 120 grit for the final sanding of the front of the panels, just to even out the joints between rails/stiles.

Anything else to watch out for?

I know I'll learn more about which grits to use in which scenarios as I use this machine, but I thought maybe y'all could help me jump start the process before I start sanding tomorrow.

Cheers,