Espresso,
I have never been to that track but I know that is a 1/8th nitro track designed for larger cars. I think the surface would be fine for the 12R5 but I would be worried about the visibility of the car on the track. I have been in this hobby/sport for 28 years and I have done all the common classes of cars including 1/8th. At our track if you put a 1/12th next to the inner pipes at our old track the 1/12th car would not be visible at all. If a 1/8th scale car came booking down the straight a 70mph and hit the 1/12th there would be mega damage, angry drivers and potential flying cars. In practice this could cause some concern. In reality since I've never been to that track and since I don't know the track policies I can't say for sure.
I can tell you though that a good speed for a 1/12th electric car is roughly
40mph and a 1/8th nitro can go about 70mph. The closing rate of the nitro on the 1/12th would be very hard on the drivers.
Steve