What Heat Range Spark Plug for an Athena Big Bore Kit?

I recently bought a 2011 WR250R with a 290 Athena big bore kit installed. I've been going through the whole bike while I'm still snowed in and when I checked the spark plug it had what I considered to be too hot a plug for the modified motor. The stock motor calls for an NGK CR9EK.
What was installed was a CR8EK which is a hotter plug. The big bore kit raises the compression ratio by more than a point and by rule of thumb the heat range of the plug should be dropped by by one heat range to compensate for the bump up in compression and it's added heat so in theory the plug should be an NGK CR10EK.

Does anyone know what heat range plug Athena calls for with this modification?

Does anyone know where I can get the original installation guide that came with this kit?

The prudent course of action is to check with Athena themselves, but if they don't specify a change in spark plugs, I wouldn't change from OEM.

I'd like to contact Athena but haven't found a ph. # or email addy.

Athena is an Italian company, you can contact their US distributor in Florida.

Just a follow up should anyone else come across this, I talked to Carl at Pro Cycle and a rep at Athena both say the kit should use the stock heat range plug. Carl pointed out that the Athena cylinder has a larger water jacket which helps in the dissipation of excess heat generated by the additional bump in compression.