I replaced most of mine two years ago including this particular one. I didn't drop the tank and chose to struggle like a barsteward routeing the new pipe close to the O/S chassis rail and away from the gear linkage as mentioned. However, I did have it on the ramp at the time and can fully understand why most people drop the tank.
4 Months ago I replaced my petrol tank so was able to 'finish the job properly' and cable tie the pipe securly, thankfully the pipe had been away from the linkage but as I say, therein lies the danger when opting not remove the tank.
Getting the unions out the brass '3 way splitter' was also a pig but as I was replacing the rears as well I was able to just cut the pipes and use a ring spanner and vise grips to remove the unions.
Use Cupro/Nickel brake pipe (Kunifer), it's a little stiffer so stays where you put it, all the unions are M10 male (think they were the slightly longer ones with a 'lead')
similar to these but check:
http://cgi.ebay.co.uk/MALE-BRAKE-PIPE-U ... 3a5b371c23" onclick="window.open(this.href);return false;
Martin