I naively started making my tallest glyph reach the ascent, but then I found that this made for 0 line spacing. Then I tried to change the ascent in the Font Info... but that changed the EM size and I'm told that TTFs need to have an EM of 2^n. So I doubled the EM to 2048, then resized all my glyphs by 140% or something. This seems to have gotten my line spacing, but I'm concerned about the behaviour of the font in editors. Of all the 7-bit ASCII characters for which I've made glyphs, there are only encodings for uppercase chars and 5 lower case ones. No numbers or punctuation. However, when using the font, other chars are still rendered. When they are, the cursor becomes much bigger and the line spacing increases and it's all got me wondering if I know what I'm doing.
Here are some samples of what I'm talking about. One image shows only the glyphs I've encoded: the other shows the same with a 0 which I haven't encoded. The ascent is 1638, then descent is 410 and the EM is 2048. None of my glyphs go below the baseline. Am I doing this right?