I am casting my mind back to Tango, which used zipties to hold down the batteries as well (interestingly, they were also NiMhs though it did also have a HDPE base plate that they were tied to which was bolted down). We did that with the LiFe batteries I lent and they may have stayed in position during the fight but they were a bit of a pain to get out, especially with them all puffed up. The ties made them awkward to get out as I recall, think we ended up cutting them because we didn't want a smoke show in the pits.