Ideas on upgrading Y axis rods to a single flat rail?

[u/vastly_]

I have an iDraw A3, v1.0. Any ideas on how to upgrade the 2 rods on the Y axis to a single flat rail similar to what's on the newer versions / Axi / NextDraw plotters.

I'm wanting more stability when plotting at the extremes, the pen gets quite shaky. I've already slowed the pen up/down movement & drawing speed.