I have found that my workouts on the Concept 2 rower have dramatically cut down on calf and AT pain. The rower forces the AT to flex and stretch as you slide forward to begin the stroke and back to finish the stroke. It is a very smooth motion that allows the tendon to warm and stretch in a continuous cycle. The days following a VFF run is when my AT is most sensitive and at times I limp slightly to favor it. Yet after a 30 minute session with the Concept 2 the pain is totally gone and does not come back. I really think that the rower has been instrumental in my transition to minimalist running. I have also found that by wearing my VFF on the rower I can also work the ball of my foot and toes as I push back on the stroke. Just thought I would share.
I have been slowly working up my running with VFF (I run with regular KSO). I started by jogging 400M and over the weeks slowly upped the distance. I work from home in SoCal so I spend most of my days barefoot, in VFF, or flip flops. Now about 4 months in I am up to 1.5 miles on a mix of hard-pack trail and asphalt road and do not experience any pain during the actual run - other than a blister sensation under the right big toe. I don't actually get a blister but feel that if I pushed another mile I definitely would. I think my KSO's are one size too big and will size down on my next pair (whenever these wear out LOL). After each run I stretch the AT and calf muscles well and follow with ice 2x for 20 minutes.