Saw that... hmmm...
Hi LJK
Pretty cool article. The point about Trojan planets is interesting because Theia - the Moon-making impactor - was thought to be an Earth-Sun Trojan, and it wouldn't surprise me if that's what whacked Uranus over and where Titan and Triton come from. Theia would've been unstable because the mass ratio between it and Earth was too high - has to be less than ~ 1/45 to last. The Jovians could easily balance Earth-scale masses in the 47 UMajor system. Uranus couldn't in ours and perhaps that's why it was rammed.
Adam