If staying with a standard ct9 an ARC or RX7 topmount would be fine IMO. If you are going hybrid or bigger turbo then front mount. Most people get one for the looks if they are on a standard turbo.
stock ct9 would produce more heat than a larger turbo 99% of the time. so its as necessary on a ct9 as a tdo4.
ive had an arc on mine and decided its best to go front mount if your at 1 bar or so
But the turbo has to fill a larger volume so has to work harder.
The standard top mount is good for 0.8 bar, Rex one i'd say 1 bar CT9, an ARC however is perfectly fine for a CT9 Hybrid 1bar, 1.1bar etc.. some blitz turbo's too k24 etc.
I dont see why anyone hasnt tried a td04 at 1bar on an ARC, would be nice to see.. would produce the same if not less heat than the CT9 at 1 bar wouldnt it?
i cant see that one at all?