Oil return mod b25ss 1971

[BEEZABUCK]

I'd like to sort an issue with the oil in the main res under the tank on oif b25ss..ie that the oil return doesn't pass through it, the oil just sits there doing nothing.
I heard years ago about a mod using an additional feed hose coming off the main return above the filter and fitted into where the drain bolt is under the seat,

It used auto brake line and fixings which happened to be the same threads as the drain bolt, can anyone tell me the parts required and sizes please as I have long forgotten.
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Also, if this mod was connected, would there be a problem with the weight of the oil in the frame under the seat/tank causing problems with preventing the return feed and cause wet sumping. The present return feed comes out at the dipstick above the oil level whereas to mod would join in at the lowest point in the rest. Look forward to hearing from you, many thanks in advance.