To be fair, it shows max distance just fine already, however Advanced Fluid Handling has underground pipes with multiple and non-standard connection directions (such as corners and t-junctions, etc) and I was wondering if it wouldn't be too hard to support this behaviour.

If not, it's fine, I can still use this quite well by simply rotating the item while it's still in my hand.

Ooh, neat mod.

Unfortunately I can't. The method I'm using to display the indicators is very inflexible. It might technically be possible to do by making large custom sprites for every type of pipe they add, but they would not be able to adjust to length changes (and Advanced Fluid Handling has dynamic lengths), so would only work as long as the mod configuration you're using doesn't change.

If there's ever a modding api update that lets me do this at runtime (I've requested it but it's very unlikely to happen), this could be added in easily.

Ah, that's unfortunate. Still, the two are perfectly useable together, and thank you for you work.