I have no experience soldering a vessel containing ether but I would imagine that any vapor pressure would increase with the heat from the soldering process, it may still present a problem at the last solder joint?

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy