Greg Guarino wrote in
:

But I'll be cutting through 1.5". It it "bad" to be pushing
the chips down in that situation? Or perhaps there's plenty of chip
room because of the oval hole? (Of course I won't attempt to go
through the whole depth at once).

Basically, yes. The advantage of the upcut bit is that it
throws the chips out of the hole. Anything else, and you'll
have to stop every so often and clear the chips out (which
is how it was done in the old days, when we only had straight
bits).

And is there any need for a compression bit here?

No - that's for when you need to cut both sides of an edge
at the same time.

Can
I further assume that only Carbide is of any use for *any* router
task?

That would be my opinion. Can you even buy HSS bits now?
I can't see any reason not to use carbide bits for all
purposes.

John