Gave up on making cannons. KAL overclocks + lithobraking is the way to go for the island speedrun. In this run, the kerbal is going so fast that he passes through the entire airfield before getting slingshotted backwards and landing directly on the airfield. Kraken lithobraking is ridiculous. 5 second time is based on the 2 second island hit + 3 second kerbal last bounce hit.

Also uses the engine plate occlusion glitch which lets you go underwater without any drag. I wasn't actually trying to go underwater since it cuts your engines and slows you down a bit (due to no thrust), but this run tied WR so I might as well submit it.

I'm sad that I wasn't able to record my very first run since somehow the lithobrake got my kerbal to land on his feet without bouncing and would have been like 3-4 seconds, but oh well. I don't think I'll ever have luck like that again in my entire life.