Historically regions have run both one day and two day regional at Lime Rock and the cars count have often been higher at the single day events than the two days even though the entry fee was often the same. I have spent a lot of time asking drivers about which events they prefer because this never made sense to me, I prefer the extra track time of a two day event. What I found was a large group of drivers preferred the one day. They did not feel there was enough track time on Friday to justify the day off of work and the expense of staying over for the night.
I think NNJR has come up with a brilliant idea. The $290 one day is about as good a deal as you can get at Lime Rock in this day and age and the Friday test day with 4 run groups will give a lot more track time that the Friday of a two day regional would ever give and is a better deal than the typical Tuesday test day.
If you figure about half the drivers will run the test day the entry income to the region to pay the $53000 rent and other expenses will be about the same as running a two day regional at $400 bit this way you get to choose whether to race for the lower entry fee or get the maximum track time.