Not good. You could exceed the maximum recommended aft CG limit for normal flight.

And Jerry, I appreciate your suggestion about a red plug. I'll do that.

Without knowing the effect, it very well could be.

It should be high on the list of concerns for anyone doing modifications that add weight to outer positions on the airplane (such as tip tanks, outboard aux fuel tanks, etc.).
Once flight testing (which I know you are doing, because the resultant handling is the primary purpose you are doing it) has proven that there are no negative influences, then the concern can be set aside.

My concern is that a thread like this might cause people to take a casual attitude regarding polar moment of inertia influences. The are very real and are fully capable of transforming an airplane with good spin recovery in to one where there is no spin recovery.

CG vs Polar Moment of Inertia
 

Just be very aware that while 20 pounds in the tail results in the same CG as 68 pounds in the passenger seat, the polar moments of inertia is significantly greater for 20 lbs in tail (approx. 2200 lb-ft^2) vs 68 lbs in the rear seat (approx 650 lb-ft^2).

Test thoroughly!

Skylor

Thanks for your concern. Yes, the moment of inertia is greater with the tail ballast and after testing at gradually greater weights at altitude I have determined that the 20 pounds of ballast changes control response in yaw and pitch and I am pleased with the result. Next project is to DECREASE the roll moment of inertia.

Respectfully
 

What Skylor and Cheif pilot are respectfully trying to shed light on, is that if you entered an accelerated spin, the 2200 ft-bs vs 650 ft-bs might flatten the spin to a non recoverable point. The extra inertia will pull the tail down/raise the nose if the spin rate was increased either accidentally, or on purpose with ailerons.

Please wear your parachute, while testing thoroughly from a very safe altitude.

Best of luck!

Just an idea
 

I'm thinking maybe there could be a way to jettison your extra weight if you were to forget. Maybe a electric solenoid or cable operated valve on the drain tube. Just a slot cut in the tube with an aluminum blade, a small return spring and a light cable or something.

Brenden, have you priced lead shot lately! I paid $60 for 25 pounds!

I took the plane up this morning and tried everything I could think of to put it into a flat spin. (By the way, an accelerated spin is not a nose high spin. And it is one of the easiest spins to recover.) I started at 11,500 feet and recovered at 5000 feet. Tried it three times, both directions, with and without aileron input, power on and off. Bottom line... it flies great! And, yes I always wear a chute when doing aerobatics. Is Bill McLean the only one who agrees that this is a good thing? Are there no more experimental pilots out there? Jeeze!

(OK, rant over. Thank you for your patience.) Out.

I don't think asking questions about your design process and thought process is bad and I haven't seen any comments in this discussion that would imply such a thing. I'd submit that asking these kinds of questions are in fact the kinds of things experimental test pilots actually do as bolting a modification onto the airframe and launching into the wild blue yonder went out of vogue quite some time ago.

You have clearly done the flight testing to validate that you still have sufficient positive stability to meet your needs. Considering that many RVs go through their entire phase one in essentially "point A to point B" flight as you described it earlier, I think you're ahead of the game. Thanks for sharing your idea and engaging in the conversation.

What do you think?

I'm wondering how you will turn the aircraft on its side to shake that shot out the little hole :D

There is a drain tube on the bottom of the box. :D