vandersteen 2sigs to magnepan .7 good move?

Eminent Technology LFT-8b. There are a used pair in Washington state right now on U.S. Audiomart for $1800. Magnetic-Planar push-pull design inherently superior to Magnepan’s single-ended models. 180Hz to 10kHz from a single driver! Woofer below 180Hz, ribbon tweeter above 10kHz.

The .7's, like any dipole (including the ET LFT-8b), need to be a minimum of 5' from the wall behind them (because of the precedence effect), in your case the 13' one, the speakers firing down the 16' length of the room. Because of the figure-of-8 radiation pattern of dipoles (with a null to either side), the speakers can be very close to the side walls, with tweeters on the sides (inner) away from the walls. With a listening distance of 8', that leaves 3' between the lp and rear wall. Use dispersion behind the speakers, and absorption behind the lp.