My thoughts are......
There are 2 long straights in that set and you are replacing 1 of them with the ARC AIR powerbase/track.
Replace the other long straight as well - If you use the ARC with a tablet/phone then the lap counter is not needed..
Add 1 x C7018 1/2 straight track (with start grid) to the side with the ARC Air powerbase and match with replacement track on the other side.
So the other side would have a C8205 straight (to match the powerbase track) + 1 x 1/2 straight to match the C7018).
(Note: The C7018 tend to be sold in pairs so you could use that opposite if you were not bothered about having start grids on the other side of the track as well)
You can of course make the straight sections as long as you like and could include both of the long straights opposite each other, just dont connect any power to the original power base.
Hope that makes sense .......