Wanderfound

Or something similar but smaller: https://kerbalx.com/Wanderfound/Kerbodyne-Aqua About 5,000m/s ΔV when fully gassed up.

It's an old design of mine, so you could argue that it's not original, but: https://kerbalx.com/Wanderfound/Kerbotruck-Interplanetary Long-range self-refuelling laboratory hydrofoil flying boat SSTO. Or you can strip out the cargo bay contents and use it as a reusable heavy-lifter.

The Sparrowhawks will crack the sound barrier, but it takes them a while to get there. It is possible to rip the wings off them, but you have to be trying hard; it takes a sudden 15g low-altitude turn at maximum speed to do it.

Sparrowhawk Mk4: https://www.dropbox.com/s/w0xf45c410h0n2p/Sparrowhawk Mk4.craft?dl=0 3 engines, one GAU, two missiles, three flare dispensers. Should be just over 4,000kg empty.

Turn off ground scatter? Sparrowhawk Mk4 on the way.

Yup. If it doesn't work, maybe Mk4 will be heavier and upgunned.

Sparrowhawk Mk3: https://www.dropbox.com/s/bpki8pw8ons1gnk/Sparrowhawk Mk3.craft?dl=0 Two engines, one Vulcan, two AIM-9 and three flare dispensers for 40pts.

Sorry about that, I thought it was clear of the weight limit. I'll update it.

Sparrowhawk Mk2: https://www.dropbox.com/s/w6kmvg97mtjevw7/Sparrowhawk Mk2.craft?dl=0 Two engines, three Vulcans, two AIM-9 and four flare dispensers for 55pts. And I've lowered the wing to provide as much tail clearance as possible; any further improvement to the rough-ground takeoff performance would require larger landing gear.

I've just realised that Sparrowhawk Mk1 actually has 65pts of weapons/engines, not 55. Revised version on the way.

It was a rush job, I didn't name it properly. Call it Sparrowhawk Mk1.

Here's a quick submission to get things started: https://www.dropbox.com/s/o1f8ry4c2hzyii6/Juno Fighter One.craft?dl=0 Three engines, two AIM-9, two GAU-8, one flare dispenser. 55 points, 4,000-6,500kg class.

Looks fun. As above: are multiple Junos allowed or not? I'd suggest that a single-Juno limit would be more interesting, but it could work either way. You might want to ban torque wheels and require cockpit torque to be disabled; tiny planes can manoeuvre on torque alone if you allow it, so you end up with flying bullets as the dominant airframe.

Imgur album: http://imgur.com/a/jmfdGAl 33 ton 56 part bomber with two RAPIERs. Hydrofoil seaplane SSTO. 7 ton payload of eight bombs. Qualifies for Battleduck (20pts), space bomber (20pts), worldwide coverage (20pts), Service Ceiling (15pts) and Airshow Manoeuvrability (10pts). Top speed of 1201m/s for swift payback (2401pts). Time of 14min 2sec for fastest bomber (10pts if so). Engine maintenance -20pts for two RAPIERs. Part maintenance -0.02x56 = -1.12. +100pts for math is not fun makes the total 2,574.88

To add some variety, how about a subcategory for Tier 6 ships?