I tried this. And engine to sun oriented variant, and overshadow craft from sun by 10m heath shield .. Ablator all time degradate.
PS. Mission consist in ecliptic orbit on sun with periapsis ~990000 km (dV 4000m/s) and apoapsis on Kerbin orbit, take scientific data (x11), fly 3 times around sun (synchronize rendezvous point), correct this point (dV 20 m/s) and reentry Kerbin atmosphere on ~5000 m/s (2 times to break). All good, but ablator to this time degradate to 0.