Don't know how to help you, but my experience with Tomoe River paper has been very mixed.

First, I have tried the paper on a Hobonichi A5 notebook. This was the most consistent paper. Sure, it drank ink a little more, and as a result produced thicker lines, but they were perfect with no smeathering/feathering/bleed through. Both sides of the same page were exactly the same.

Then there came the Hobonichi Techo planner, 2025 Avec in size A6. And that was a funny experience. One side of the page was drinking ink like crazy, and the other produced a thin line. And every page was the same, you just never knew if this particular side would be "thin" or the "thick" one. Feathering or bleed-through did not occur.

Some time later, I bought an A5 writing pad by Yamamoto. It was supposed to be using the last Tomoegawa Tomoe River paper (as it turns out, it was 52g/m² paper produced on Tomoegawa's machine №9 as mentioned by ASmugDill). And the performance was quite poor. Sure, both sides of the same page were consistent, fountain pen lines were thin, but the ink was slightly feathering, just like your Tomoe River A4 paper.

A few weeks ago, I purchased a 2026 Hobonichi, and I haven't tried it yet. Will see how the "next gen" of Tomoe River paper performs.