if the snrm drop is so high it's causing a resync every time, and 42 just didn't cut it, you could try somewhere in the middle. perhaps connect when the crosstalker isn't online, but limit the sync speed to say 50mb rather than 55mb. this might be enough to hold the connection steady when your neighbour connects.
It's not the full 55mb, but it's better than 42mb. If you don't know the command to limit the sync speed on your modem then just tell us which modem you use. The command is different for different modems.