Squibbler
Sorry - didn't mean to faze you! Your comment was spot on and I assumed that you were an ATCO with a PPL; btw I don't buy into the "lowly" ATCO statement, we're all on the same side!
5-6 degrees sounds steeper than it is in a light single; its the same angle that is used at London City and whilst it looks impressive for a 146, a PA28 or Cessna can manage it easily.
As a rough rule of thumb that you might find intresting, to make a 3 degree glideslope halve your groundspeed and add a zero - so approaching at 70kts, 350 fpm would be required (or 300 feet per NM... divide by g/s and then multiply by 60)
To hit a 6 degree slope at , this figure becomes 700fpm/600per nm, which you may recall from your C150 days is circa a glide approach. Obviously, the stronger the headwind component, the less the rate of descent required to maintain the glidepath.
The PPL syllabus focuses on powered approaches for normal landings which is why your instructor will have taught you to to use the PAPIs in your training, but many of us use steeper angles to add a safety margin in case the engine has problems near the filed; unlikely, but it all depends on one's personal view of risk!
I would not land before a displaced threshold - if the field is not long enough, pick another one or another aeroplane with appropriate field performance!