I am no expert - but from the info at the convention:

Today there is no FESSL over 13.5m - it is a weight issue. the FES sustainer comes in 15m & 18m . There is one new Polish 13.5 with Electric motor on a boom, also self launching.

the 13.5m seem to have gained glide ratio - going from 37:1 to mid 40's:1 (if you believe the brochure.

I am also inclined to believe most people will opt to aero-tow with more reserve to get home - but having an option to fly on a weekday when no one is around to tow???? inviting, no.

WH1