Honestly, my builds will go BIG! And I mean big. When you want to launch a 600,000 ton payload into orbit all in one piece? Come to me. With Starship Alpha, my flagship of my fleet of interstellar transfer vehicles, its the largest of its class. This payload weighs in at over 600,000 tons and is comprised of over 2000 parts. Heavily modded save file, I will warn. The mods that I use are as follows (the ones I can name off the top of my head): Mechjeb, Kerbal Attachment System, Kerbal Inventory System, Kerbal Space Program Interstellar Extended. Tac Life Support, Kerbal Engineer Redux, Extended Hanger <--- (craft would be impossible to build without it), Planet Shine, KoS Scriptable Autopilot, Kerbal Star Systems, Copernicus for KSS, EVE (Environmental Visual Enhancements), Kerbal Station Parts Expansion Redux (Centrifuge modules are from this), Hull Cameras, Strobe Lights, Grounded Ground Vehicles, Flexodocking Flexible Docking Ports, Planetary Base Expansions, and some others that I can't think of right now. Also, does anybody know what the largest craft that was ever built is? I don't trust those Youtube videos as claiming to be the largest.
P.S. I will include photo once I can get it. Photo is of Starship Alpha, not the others in the fleet. Starship Alpha is the largest of the fleet and the largest craft I've ever built! Makes me so proud that I got this thing into orbit all in one piece, no orbital construction required!
P.P.S. I don't think I can include the precise weight, mass, length, etc.; Because Kerbal Space Program doesn't load the VAB on that save file, LOL. Probably because it's too busy calculating the constant trajectory of that behemoth in orbit (I haven't sent it interstellar yet since it's supposed to stay there until the rest of the fleet arrives in orbit.