I have a NSL fleet from GZG. I use this as my reference fleet for determining mass for ships from other ranges. Basically, I compare the size of the different models and pick a rough mass range.
For the Trek ships, I have used the models from ADB. I use the fleet scale ship diagrams to determine the weapon fit for the ships, adjusting size and arcs within the mass limit.
I use FT beams for Trek phasers and pulse torps for photon torps. Note, all my ships also have a couple of shuttles. These come free with the ship, like crew. They are not troop transports etc as described in he FT rules. They represent life pods, small interface craft, or a limited bording capability.
Here is the Federation Constitution Class Heavy Cruiser aka Enterprise.
I do, however, have a couple of related ships.
The "Strike Cruiser" is a minor variation made more for war than exploration.
The "new fast Cruiser" is another ship built for war. Specifically deep raiding.
Some smaller Federation ships.
For now, my enemy fleet only consists of Klingon F5 frigates.