Tamiya Championship Series

I don't see a rule about battery stays/holders. When using a shorty pack in M-chassis are there rules around what can be used?

Tamiya rules are especially peculiar about this, while they still usually vary greatly between countries. And non-Tamiya parts seems one of the major on-going themes that are more or less consistent nevertheless.

Tape, adhesive, foam, oil, grease, glue are generic expendable items.
battery tape has been used for years, dates back to NiCd/ NiMh. TRF415, 416, 417 didn’t have battery retainers so tape was used. So tape is legal.
3D printing a part to substitute a battery holder to fit a shorty pack, is creating / designing a specific aftermarket part for the M07 / M08
battery tape has been used for years, dates back to NiCd/ NiMh. TRF415, 416, 417 didn’t have battery retainers so tape was used. So tape is legal.
3D printing a part to substitute a battery holder to fit a shorty pack, is creating / designing a specific aftermarket part for the M07 / M08

M07 is a bit heavier.

With the M08, I wanted the side-to-side weight distribution that a full size pack provides.

Tape, adhesive, foam, oil, grease, glue are generic expendable items.
battery tape has been used for years, dates back to NiCd/ NiMh. TRF415, 416, 417 didn’t have battery retainers so tape was used. So tape is legal.
3D printing a part to substitute a battery holder to fit a shorty pack, is creating / designing a specific aftermarket part for the M07 / M08
battery tape has been used for years, dates back to NiCd/ NiMh. TRF415, 416, 417 didn’t have battery retainers so tape was used. So tape is legal.
3D printing a part to substitute a battery holder to fit a shorty pack, is creating / designing a specific aftermarket part for the M07 / M08
So is that the official rule from FMW? or is that our collective, educated assumption?

I'm experimenting with shorties on the basis that mass centralization is "good". I've added weight to bring it up to par and... so far so good. Had to chase setup a bit, but rotates well. You have to plug in your batt before sliding it in, so that is a bit of a pain.

Does anyone know if the TRF420 C-hubs are a direct fit for older models TRF417, 418 suspension? TIA

No unless you ream out the hinge pin hole from 2.6 to 3mm which I don't think is allowed in TCS rules but is physically possible.