If you do a good valid range check, determining the Baseline comparing that distance with full power you'll know what difference internal, external, full whip, or loaded whip makes before you ever go airborne!

During the design phase, and possibly with a little more work after construction, you can route the factory wire antenna out the leading edge of a wing like BV does in the BobCat. Bob may do this in other Jets he produces, but I can tell you the leading edge of the wing is a great location for the antenna!

If that's not an option, rather than a full length whip antenna standing straight up (which does look toyish), route the wire antenna to the rudder like we all used to do for many years. To me that looks much better and more like what you might find on an aircraft. Shoot I've got two external antenna's on my MIG and over the years I've gotten to like the way they look.
Lee H. DeMary
AMA 36099