Started playing with the bit yesterday. Tear out an issue on the poplar I was using, but manageable by machining the joint on a board 1/4"-1/2" wider than you need, then ripping to final width, and cutting off any blow out. You could back up with sacrificial pieces of the same thickness when running through the bit, but that would be more work and likely in the end more wasteful?
Interesting similarity in the way we maneuver around 'end tear out'.
I have only used a sacrificial backer a few times, just often enough to feel like I know how to do it, if and when it's needed in the future.
I have cut a joinery groove into full length boards (4' to 8') before cutting it down to the lengths that needed.
After MUCH trial and error, got the 2 sides to match up like they should. Lessons learned: 1st atempt using just a mitre gauge and a feather board to guide was a complete failure. Combination of the large bit and small work pieces necessitates a rock-solid method of holding the boards in a vice-like grip. ANY movement--up/down, in/out--and the joint is compromised. By end of the day, it became obvious that I was going to have to make a specialized jig for my cheap little Sears router fence before I could get acceptable results. Have a pretty good idea what I need to make that work. Will check out the videos you suggest, and report back with any new results.
Perhaps feathering both sides of the board from the top down so that the edge away from the bit can't rise up would help. Dual feathers pushing it down and a third holding it up against the fence would have a way of keeping tit controlled.
The profile's of this kind of bit don't allow much flexibility for doing it in more than one pass over the bit. Depending on the variables it might be possible to do a little pre-cutting on a Table saw to reduce the amount of waste wood that needs to be ejected during the 'fancy cut'.
I had read in an article somewhere that best results in the context of 'smooth cuts' were obtained with 3+ passes. I don't remember what the stated rationale behind the first 'micro-cut' pass was, but the writer suggested a 'teasing first pass', followed by hogging passes (as many as required) and ultimately a fine cut final pass.
Just thinking out loud here. Time on this board has taught be that just throwing ideas out has a way of inducing others to chime in with their 2 cents worth..