Alon c90 oil change

I pulled the quick disconnect drain plug all the way out. No additional oil came out. The dip stick still reads about a quart.

so the total removed was 1 3/4 quarts and the stick read almost 4qts before I started

I know I’m not getting all the old oil out.  I know this engine was designed for taildraggers. Nose high, tail on the ground.  Which may aid in draining all the oil.   My aircraft came to me with a push style quick drain installed where a plug should go.  But even when I wire up the drain bucket and hold the tail to the ground.   I only get about 2 quarts out.   The dip stick still reads 2 quarts after the oil has been drained.  

i have no idea how far the quick disconnect threads into the oil pan. 

Anybody have a clue?   Removing the lower cowling every oil change doesn’t sound like fun.