Just a comment as to why 3.5 degree glideslope PAPIs are not suitable for light aircraft. All airfields have a degree of windshear assocaited with the approach to a runway. You have probably noticed that between about 100 and 300 feet the aircarft sinks a little (or a lot on a windy day). The degree of sink will depend upon the time you spend in the windshear zone. A heavy ( and thus fast) aeroplane transits the zone quickly and is less affected by the sink. A light aerplane doing a groundspeed of 50-60 knots will stay in the zone for longer and will be affected by it for longer...causing more sink. End result...potential undershoot and the need to add power...and destabilise the approach.
Much better to fly an a steeper approach or to land further into the field (if this is an option). As an instructor I have taught many people to master the approach...and one of the first things I always say is ignore the PAPIs, stabilise the approach and look to see that you aiming point remians constant in the window. Also as the wind and windshear increseas, aim further into the runway for touchdown. There is currently a discussion about this on the instructors forum at the moment.