Hung, Well to be honest, Yes it does take practice, I do the nines in pairs, niner niner, niner niner, seven. Also both aircraft end in 7 so that helps. N99997 is an Ercoupe. Been working on restoring it for the past four or five years and getting close. Wife says I need to sell one of them when its done. Guess it will take me a couple of years to decide which one I will part with. You know, got to get a couple of hundred hours on each to see which is best. :-) By the way N99999 is also a Coupe
and lives in the Boston area.