Well that's an interesting setup tubasteve....
I have relocated the oil filter to 2 spots in the past.
The first was where the water to air intercooler pump would sit (under the battery)
The second is behind the indicator on the bumper (right hand side of vehicle)
The best real world advise i can give you is to use -8an lines and fittings and if you use an oil cooler dont go larger than 10row.
I have -10an lines and fittings with a 12row oil cooler and i get really bad pressure drop when coming to a complete stop or idling on an inclined surface, without 2 oil pressure gauges watching 2 different areas i wouldn't have kept my car alive for this long.
Keep in mind this was originally done when i had a full engine rebuild back in 09 so me and the engineer had time to figure stuff out
The oil pump gear was changed, the unit now flows with more pressure, this is offset by the entire oil system being larger in volume...oil pressure is very close to stock.
We blocked the water bypass hose off so no more hose from hell to deal with, from now on 100% of oil cooling comes from the external oil cooler and not the stock oil/water cooling unit which is honest to god poo.
Cuts were made to allow the large -10an hoses to pass thru small holes in the engine bay
(you absolutely must cover the shiny steel braided hose with a a piece of rubber hose to stop it from vibrating against other metal surfaces, if it does get metal on metal vibrations u will split the hose quick smart....another hard lesson for myself...hopefully not for u)
Here are pics of both installs, i hope they help....pay no attention to the wrx oil filter
another sacrifice i had to make