Liquid Surface placer off by one at coast

[jagprog7]

I have a structure which should just break the water's surface (like a boat). Left side of image is intended. Right side is not. When the structure spawns overlapping the coast (rare case, which can happen even if restricted to Ocean Biome), then it is placed one block lower than the placer is configured for.

A fix or workaround would be appreciated! Desired behavior: placer should have consistent behaviour.

Default "Liquid Surface" preset + a Baseline that makes sense (in my case, 8).

Minecraft: 1.12.2, latest forge + this mod

(in the image, I generated it manually via /#gen, but this will happen naturally as well).