ArtW
I fly a 14 1/2 lb AV8R with the PST J600 and have a 50 oz main and the standard BVM UAT. I have a 10 oz overflow tank attached to the vent and use it to taxi to the preflight area. I set my talking timer to 7 min and then I remove the overflow tank prior to take off. I have my flight routine down so that the mains touch the runway when my timer tells me zero time is left. After taxing back and with the shut down procedure, I have the UAT full and approx 5 to 10 oz still on board, depending on throttle management through out the flight. This fuel capacity is fine for the J600 but I would recommend at least 60 to 65 oz for the J600R for approx the same flying time which will give plenty of reserve.

RH