Nice work Commander X. Here's my own, slightly 'broken' design, for your players to play with, if one should chose it

Variety is good right. I say slightly broken because in T20 you have to have both a minimal 4T bridge (I call it a helm) and computer (unlike HG which allowed you to choose either or both). Based on the design rules of half the bridge being the c&c and the other half filled with whatever, I've loosely interpreted it as so for small craft helms too. I've also used a bis* computer (not allowed in HG but apparently OK in T20 unless I missed the note) to compensate for the upgraded streamlining and avoid the agility penalty.
(* hmm, come to look at it again I seem to also have bis model computer cores and avionics as the same size and all as the std model computer core and avionics. It's a house rule so that bis computers are the same size as they used to be in HG, more or less. It also meshes with my house rule of matching the avionics model number to the core model number, for the same reason. Other computers would be optimized, not standardized, imtu and so the ship/craft would not be eligible for the 20% standard design cost reduction)
Gnat class TL13 Interface Fighter
+8.0T Hull - Needle - Fully Streamlined
-0.4T Upgrade - Airframe (folding wings)
-4.0T Helm - std - 2 seats
(1.0T Computer M/1bis - included in helm)
(1.0T Triple Weapon Mount - included in helm)
-1.1T Maneuver - 5G - Agility 5
-1.3T Fusion 13 - 1.3EP
-0.1T Fuel x 2days
-0.8T Armor 4
-0.3T Magazine Autoloader/Bomb Rack
The ship includes fuel scoops and is armed with a light laser (F2 x1 - mining laser) for defense and vehicle combat and double missile launchers (F2 x2 - missile) loaded with 6 missiles total. The magazine carries 6 more missiles which can also be simply dropped as bombs if desired. Alternatively the magazine can be used for cargo, extra fuel or fitted for standard bombs or other small weapons. The Gnat is not suitable for long missions as there are no facilities for the crew beyond what their suit provides. The cost is Mcr10.5712 after discount, not including missiles.