OK, I've been a slack moderator & not watching this section ('cos you are all so well-behaved here & rarely need chastising :D ). Nah, I've been slack, I'll admit it...
Just sent a reply to a PM from Matt concerning his dovetails which are causing him some concern. As I said to him already, you have to think (ahead) in three dimensions in this game. He's cutting his joints the opposite way from the way I've shown in my 'manual', & I think it has caused some of the confusion - the steps in my 'manual' wouldn't make sense in that case. However, I don't think it's a game-stopper. The way Bill carter does his mitre planes is to put "pins" on the sides, & 'tails' on the sole; it's the only way you can do it with continuous, bent sides as on his planes. It looks just the same when it's all banged up, & does the same job. Matt just has a slightly more awkward job when it comes to scribing the tails to the bottoms of his sides, but if he uses a block of wood, a couple of clamps, & four hands it'll be fine. :U
Dunno what I'd call the sole join you've used - a birdsmouth? TBH, I reckon it would be more difficult to do well than a tongue & groove joint, so I dips me lid to you, sir. I found the first one I made much easier than I expected, and it's fairly easy to cover up any slight imperfections with some judicious peening, whatever join you use. Some people just use a straight bevel. The advantage of a T&G as I see it is that if you get a good, firm fit it can hold the parts of the sole together nicely while you scribe sides. I've suggested to Matt that it might help if he silver-solders the sole back together before that step, so that the bits stay properly registered while marking out. Once the sole & sides are banged together, it doesn't matter what join you used, the sides keep it closed up.
Anyway, as Ck says, just soldier on - I was close to giving up in despair several times on my first infill, but was determined to finish the damned thing after I'd invested so much time (& pride!) in it. You'll be fine...
:)
Cheers,