Best non-fabulous diamond scrip conversion?

You can only make so many brass lollipops before going madder, so what do y'all think is the best thing to buy with rat shillings for sale as scrip? There aren't many options that lose less than 50% of their value in conversion (too inefficient), leaving, I think, just flawed diamonds and royal blue feathers.

Flawed diamonds can be bought for 2 shillings (20p), and sold for 3 scrip (15p), but it costs an action to convert in batches of 100. 25% loss I think. Feathers can be bought for 8 shillings (80p) and sold for 1 scrip (50p) but without costing an action. About a 30% loss, but infinite SPA. At the same time you can look at selling to the rat market as a step in conversion instead as the end goal, which can make either of the above options a profitable conversion . You don't get 85E per whisper/device/whatever, but you will get more than 125S for them.

So, what do y'all think?