how can i change the fixed ramdisk size of 6.66MB during runtime?

I created 3 ramdisks (6.66MB each) and filled them with airodump. It interrupts the hard way everytime the ramdisk is full. I cannot "append" those files with aircrack (file1 file2 file3) in one line. Aircrack stops after the first file with error 'unexpected end of file'. I can only process files one by one separately and correct me if i'm wrong that's not the same like doing it in one command line since the IVs (or the capturedata) relies on previous captured data that won't be used in this case.

I create ramdisks this way:
mkdir /tmp/ram1
mke2fs -m 0 /dev/ram1
mount /dev/ram1 /tmp/ram1