I'm a few kilos heavier, but would say having the 62 as the only board would be a challenge. It really is much smaller. When you're reasonably powered up and the wind is not to gusty the 62 get planing rather early and feels quite efficient. But as soon you start spending time semi sinking, you definitely notice you have 8 liters less buoyancy.
The 62 is not the same shape as the 70. The 05/06 was rather similar to a small version of the EVO 75, but the 07/08 got updated to a slightly more drivey shape. For me its a bit less natural at higher riding speed in the bottom turn. On the other hand it is noticeably easier in the cup back. Here the smaller tail really makes a difference. For general high wind control the 62 is fantastic. There is just so much less board to handle.
Maybe one solution would be to get the 62 and then patch the 70 back together for the light wind/gusty days.