SeabeeDaddy - I also have a 4x8 layout with two (2) independent ovals (although I only use 0 Gauge track - no 027) and I have 042 curves on my OUTER oval. That said, FWIW I also have one (1) STRAIGHT HALF-TRACK piece (O gauge) at the centre of each 4 ft. end of the table; and it's worked fine for several years with no derailments.
Good Luck with whatever you decide to do!