Cementitious Non-Shrink Grout - Surface Area?

[techcrete]

What percentage of unconfined surface area is allowable during placement of a non-shrink grout?

I am aware that non-shrink grouts need to be confined when placed, perhaps with a grout-box around a baseplate. However, a grout-box has unconfined surface area in the space between the baseplate and the grout box on the north end once the grout has been poured. Is there a percentage limit on the unconfined area that needs to be determined when designing a baseplate grouting application?

Thanks in advance for your expertise!