^^ soft for sure. The BDE I used to use was 15L and was super soft, and still was easy to impart spin in an 18x20 with the 1.18 MSV crosses.
Even the stiffest & thickest guts are going to be soft in comparison to most (if not all) other string types. Tonic 15/MB sounds like a killer setup with great longevity.
Many strings available to trade.
Looking for Tour Bite 18 & 19