When I had the option to do 2x/day, in GPP and into the early SPP, I kept a limited number of MB accels in the AM most mornings.
The numbers were low enough not to be a problem that way, but later in the SPP, they’d have to be done the AM of an afternoon speed session for up to mid level sprinters but prob dropped for top level sprinters except during grass sprint training as I mentioned before.
Another option for top sprinters would be:
Start off AM daily, then AM of speed day, then briefly AM of day AFTER afternoon speed, then dropped. This case might arise when there will be a long GPP/SPP period or when weather isn’t cooperating to allow speed to rise as much as planned or if injury has held down speed for a while.