Binary...
Now, go back into that HS. Start picking out the most expensive stuff--flight packs, four stroke engine, the whole works. Let the guy get his pants all wet. Tell him it's for a big spad. When he starts knocking them again, tell him to just keep all his stuff and walk out. If he doesn't knock it this time, ask "aren't you that guy who said I was stupid for building spads" and then walk out. Should be a very vindicating experience for you!