Circumnavigation on Kerbin-Rescaled to 2.5

We have some complications, however - using the FAT-455 wing solved my problem for lift and fuel space, but this thing can't withhold too much heat - so I can't sustain Mach 5 for too much time. The best compromise is rising the altitude gradually each time the vessel reaches near 1.500m/s - this prevent the part from blowing up due overheating at the same time keep a reasonable cruising speed. Had I access to a similar wing more resilient to heat, I would push for more speed.