What are the specs on your spade? Spade thickness, etc. I'm thinking about building one for by 400x, but am not sure how heavy to go. I've got a lot of rocks that I'd probably have to pry out. Would your's stand up to abuse like that? How's your soil?
The quick spade you built looks like it would really work. Do you have any other pics showing how you attached it? Any dimensions? Did you cut the pipe yourself? I know it's a long time ago you posted this.