DavT
Ive used the 115 with 7.0 and 6.2 and its absolutely great.
From there I could drop straight to a 5.3 and a freewave board.
For pure early planing in sure the 130 beats the 115 as 12-15 knots is very light conditions, but once planing (and I think the blasts do get planing well) the 115 with 7.0/7.2 in say 15 knots is super fun. FYI, In the light stuff the blast 115 also loves a slalom fin to liven things up.
So if you're 100% focused on minimum wind planing maybe the 130, but if you want the best fit board for both sails maybe 115
Im pretty much your size and to really have a good ride in 12-14 knots I would have to go a whole board and sail up from the 115&7.0, to maybe a 75cm wide freerace board like the jag and an 8.0.
In these same conditions yes the blast 130 and 7.2 will probably plane ok but it won't be particularly active & exciting.
But I like the blast as soon as it's 7.0 freeride conditions as it cuts through the water so nicely