Hi, I'm an amateur font designer with several little hits on Dafont (though they're mostly display fonts). I'm working on my first attempt at making a multi-weight font.

This is yet to be named, so I would like some suggestions on that as well. The top is supposed to be Heavy/Extra Bold and the bottom is supposed to be Hairline/Extra Light. May I get some advice regarding this font's design (besides the kerning of the preview; it's still not been assembled into a font file)?
Comments
In short, you have some very nice letters and a good sense of proportion, but there are some issues with color and harmonization. I think you'll have it sorted out in no time.
Because your glyphs are the same actual width in both weights, the Light ends up looking a whole lot wider than the Bold. Which makes certain characters look weird, some more than others. Don't worry about what the actual widths are, just make 'em look right.
Side-note: I tried interpolating on FontForge, but /h/w/x/y produced jumbled results. Any idea what's going on? I've posted this also on Stack Overflow.
This is actually really cool! A nice mix of modernist and humanist features, and some funky glyphs to stand out. The first thing I noticed is that the interpolated 'regular' looks perfect in width to me, but the extrabold looks too narrow, and the extralight looks too wide. Furthermore I recommend you use proper type design software (preferably, Glyphs, Fontal Studio, or RoboFont) if you want to make this into something truly worthwhile.
I don't really get the structure of the light v w and x, it's unnecessary.
Get the basic things right, before you start focussing on details again. Don't stop here, though, keep it up!
I recommend using trufont.github.io which is essentially FontForge's replacement, many of the key FF development community have moved their focus to it
Kemie, I'll post a note about this on the ff mailing lists now