synchronizing multiple sensors to MaxMSP; millis? interrupt?

I'm running 8 FSRs into Arduino Mega, sending serial bytes to Max; the end of the packet is punctuated with a Serial.print(255, BYTE)

You haven't posted any code to show how this is done.

it all works fine and my FSR values are arriving in Max independently and in order.

Hard to see how this is happening from the code you posted.

However, is there procedure for ensuring that FSR 1(on pin 0) always arrives first?

Send it first.

bump?

Where is the bump. Well get the street department out to fix it as soon as possible. The weather this year has been hard on the roads, so it might take a while.