It is not uncommon for the aircraft to have a problem slowing down to land and stick to the runway with the engine at idle when you have a light aircraft.

The thrust of the engine at idle (especially with some of the high power-weight ratio combinations we fly) can exceed the aircraft's minimum poer to maintain altitude. Add in ground effect and you can have aircraft flying in "the backside of the power curve" (where you point the nose down slightly and the plane accelerates and climbs with no throttle change) that just won't settle.

Lower prop pitch is often the only way to allow the aircraft to land while the engine is still running. With the lower pitch, at the same idle rpm, you don't create as much thrust. Increasing pitch and reducing diameter can sometimes help... but there are other tradeoffs when doing that, which may be a disadvantage, especially on a Cub or a design such as the Four Star which won't bennefit in (or from) top airspeed.

Being able to hold the nose higher due to a further aft CG can put you further into the backside of the power curve... and that does help sometimes. Being able to maintain pitch control at a lower speed (all kinds of explainations as to why... all add up to less downforce from the tailplanes needed with the CG change) and have the aircraft "wasting" more power due to higher AOA giving more induced drag. Caution here though... you can get in a place where the added power needed to prevent slowing to stall at that higher AOA makes the aircraft exhibit the above nose-down = accellerate+climb phenomenon more clearly...

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A book I recently found (well... given to me by my mother out of some of my father's old books...) explains why this stuff happens pretty clearly. It doesn't address being unable to slow down specificly... because the book is intended for full scale, and at idle, they never have more power than needed to stay aloft.

"The Proficient Pilot"
AOPA 1980 (Author listed in a dfferent topic here... "Great Book!"... its in the car at the moment.)