In regards to PAPIs not working for light aircraft I have never heard that before. If that is the case they would not work for the great cross section of airliners ie A380 v SAAB 340.
Also why should light aircraft make a steeper approach? It is all a distance to threshold against altitude. If you are making a steeper approach then you are making more work in the hold off and will be high on the start of final.
GFO69 - PAPIS will work for a bumble bee if he has the eyesight to see them. But even if he has, he wouldn't bother 'cause it wouldn't be appropriate.
Why should a light single make a steeper (than 3 degree?) approach?
Are you serious?
SSD