also, and more importantly,, if you pick the wrong details and combine them, you will have a chocolatey mess instead of a good flying plane. I think this is what Howard was trying to point out. You cant just pick one number from here, and another number from there, and if you just happened to pick all the right numbers from desings in the seventies, then your plane might fly as good as a plane from the seventies
it is horribly important to not loose site of the fact that an airplane is a SYSTEM of design comrpomises and you cannot just combine random "numbers" and expect success.
Like when I was racing stock cars,, there were articles all the time, "shave .5 of a second off your laptime by this trick" Heck if you implemented all the tricks outlined in those articles theoretically you would end up running half second laps,, lol and that wont work in the real world. SO remember every design is a system which has been refined by tweaks and small adjustments to make the airframe perform the way the designer wanted. Every change served a purpose and unless you know the interaction and the purpose of each variance of numbers, then yoru really just poking sticks in the dark.
My suggestion is to blatently copy a design 100%, change the wingtips, canopy, and rudder,, but leave the airframe intact..