Well, your small jets remind me of this private small jet BD-5J sold by Bede Aircraft.
This is known to be the world smallest jet powered aircraft:
http://www.koonysun.com/pics/SmallJetBD_5Jb.jpgYour models obviously seem to have nicer engines, but they are still "small" planes, so when I look at them I get the feeling that they could, if they existed in real life, barely reach Mach 1, and they would feel very light and nervous. That's why I was referring to the Alpajet, as a comparison. The Alphajet is of course more heavy and less nervous, but its performance is quite cool for small jets.