The Subaru SVX World Network - Replacing fuel lines on top of tank

Hi everyone, while sorting out my non-working fuel gauge problem (it works now :) ), I encountered something else. Crusty, weeping hardlines on top of the fuel tank. :( The bad spot (on all 3 lines) is where they exit over the top of the tank and curve down before making the connection under the car to the rubber sections that in turn connect to the hardlines that run up front through the grommet under the rear seat.

Since I don't really have the facilities / tools to drop the subframe and tank to properly replace the hard lines, I was going to just bypass them completely and run rubber hoses through the gap between the tank and the body and connect them that way. I've read through old posts on this forum where other members have done it this way with no ill effects.

I've measured the fittings coming off the fuel pump / sender unit on top of the tank, and it looks like the vent and return lines (held with spring clamps) are 1/4" ID, and the supply line (held with fuel injection clamps) is 5/16" ID. I know that I will have to run fuel injection hose for the high pressure supply line, but I'm thinking I can get away with standard fuel line for the other two, since they are low pressure lines? Am I correct in figuring that I will need 1/4" line for the vent and return, and 5/16" for the fuel injection line? I haven't disconnected all of this yet, as I don't want to disturb it too much (and risk making it worse) and don't want fuel leaking everywhere while I gather parts to fix it. Also - does anyone know how much hose I'd need for this? I'm thinking roughly 8 feet / run, but that's just me eyeballing it. Would love to hear from anyone who's actually done this. Thanks in advance for any help :)