For the kana kit, the second 1u pipe is r4 yes. Apologies for the confusing placement of it in the render (r3 row instead of r4).
Are you sure about that? The 1u
\|ム key is supposed to be R3, as pictured in the render, not R4. This is in order for the ISO/JIS kana compatibility in the kit to be correct (which is the reason why some of the other keys are in that kit to begin with). In other words, the current placement of that key in the render is totally correct.
What you could do, if you want to have pipe on R4 in the katakana kit so it matches its position in the base kit, is change the R3
\|ム, R4
<>ロ keys to R3
#~ム, R4
\|ロ, respectively. But this would require two new molds to be produced, and you would potentially have to communicate it with MiTo (who is the original author of the katakana subs that you're using) to get the vectors sorted out with GMK.
That being said, in my opinion, it's fine the way it is. White accents are an interesting prospect, though.