I do a slight variation of that.. My first calf day (which I train first before either back or chest) I do the 5sec negative 15sec stretch for 2 sets of 15.. The second day I start by doing the stretch for 2 sets 60sec. each, then I do 5 sets to failure.. After each DC-type exercise I do another calf movement to failure.. Example:
DAY 1
5sec/15sec - 2 sets@ 15 reps per..(using a donkey calf raise machine)
Standing calf machine- 5 sets to failure..
DAY 2
60sec stretch(either standing or donkey calf machine) 2 sets for 1 minute.
Donkey calf raise machine- 5 sets till failure..
Got 17" baby moo-cows after 4 weeks of 2x weekly routines, alternating each movement and order of exercise..