Dry Sump Oil Temp - I can't get it up !!

I've got my street project basically completed now (Nissan VQ37 in E46 BMW) which has a 4 stage Ed Pink dry sump pump, 2gal Peterson tank mounted in the engine bay and a Greddy thermostatic filter plate setup without a cooler at present (just has a hose maybe 300mm long as a bypass).

I just don't seem to be able to get the oil temp up past about 65 - 70 degrees celsius when driving !! If I leave it idling it might get a bit past 80 and I think the most i have ever seen was about 85.

I'm measuring the temperature at the bottom of the tank near the outlet to the pump so this is the temp going into the engine.

Have people struck this before and are there any common remedies ? I might try and insulate the tank but just so naff on a new build :P