w00t! That F5 is INCREDIBLE...*vast* improvement. I agree, I was never really sold on the SFB one. Only comment I have is...I'd make the body a TAD bigger, and the 'wings' a TAD smaller. Not too much, but the proportians right now seem....a *little* weird.
I agree about the C8/9 - the SFB ones were kinda....ugly. I sort of accepted them as 'ugly' with a certain charm...kidna like the WW2 Japanese 'Fuso' BBs with their pagoda superstructures. The double-bridge stack you have is nice, but I think a big part of the 'Federation' class is the saucer is much larger, I think I'd increase the size of the round parts of the C8/9 bridge bubble-thingy.
I think the sec hull needs beefing up...somehow. I can't think of anything right now. Maybe not have the back of it sweep in quite so much? Dunno. I can't quite put my finger on it, but it just needs beefing up somehow.
The Fed DN, too me, looks like more than just a CA with a third warp engine. It's like, every part of it is bigger, stronger, more built up. It just looks TOUGHER.