Hi Guy, and as far as why you can't make a larger radius fillet in that one place - that's caused by the "bunching" problem where you're asking for a fillet that is a bit larger than the available space for it going around a bend. In your case here since you've got the bottom part slanted that also reduces the space available more than if the end was at a 90 degree angle.

Bunching is like this - trying to make a large radius thing go around a tight bend:




So note there that at a certain size the piece start to stack up over top of one another and make a kind of chaotic self-intersecting area.

If you turn on surface control points for the 0.82 radius fillet piece (use Edit > Separate on it to break it into its own surface first), you can see that it's just about at the limit of that kind of bunching on the tight side, much more than that and the sections start to cross over one another:





- Michael