other than space are their any other benifits of an under car set up?

Not a single one.

i just dont know how u would run the oil return line effeciently

With an oil pump. It is not efficient or durable, but people do it nonetheless. Not that that should surprise you, reading the idiocracy contained in this thread alone.

Mentioned earlier in the post... The CT26 is not a great turbo or even a "good" turbo for that matter. Yes, if you rebuild one it might last for 50 to 60,000 miles at normal boost levels, however, the turbine housings crack after old age sets in. If you turn up the boost however, the 270 thrust bearing rolls over and your back at square one.

Back in the day 5 - 7 years ago, people started machining 360 degree thrust bearings into the CT26 CHRA's, but if it was not done perfectly, they failed shortly after. This is why the CT26 has been pushed aside for other turbo's over the years. The only shop that I know of that did a nice job of upgrading the CT26 CHRA quit doing it because the end customers started having troubles finding turbine housings that were not cracked badly and this killed the demand.

Also, I'm not sure what size engine we are discussing, but putting a TDO5H 14B or TDO6H 16G from a Mitsubishi Eclipse (DSM) style of engine won't do so well on a 3.0L V or inline 6 engine. If I was going this route, I would get a Mitsu style 20G and make DAMN sure it has a TDO6H turbine wheel on the hotside to support an engine of this size. The TDO6H turbine wheel is big and will flow enough to keep up and the 20G compressor wheel would be much better matched to an engine of this size. My old built 4G63 stopped making good power at around 6300 rpm's on a TDO5H 16G and that a was stock displacement 2.0L 4G63 with a good flowing head. Maybe the engine isn't a 3.0L and I'm just lost, but putting this in before you make a mistake.

rear mounts are more budget based that an advantage

How so? 12 feet of aluminum piping and 8 4-ply silicone connectors makes for a very expensive charge side. You also need an oil pump, 20 feet of oil lines, a new air filter every couple months, and everything else needed costs the same. A decent front mount will be cheaper, and more advantageous is nearly every way that matters.

you could use abs for charge pipe. $70 oil pump. high temp tranny lines for oil lines. make a shield for the filter, keep crap out. plus some front mounts require ac to be removed.

Halfass builds produce halfass performance, and cost more in the long run.

i'll agree with you on that but the stuff i mentioned is in no way half ass. shurflo 8000 series have been used on applications before with no problems. tranny lines can be used but must be shield from any "hot" spots. abs is perfect for charge its just guys out there have their mind set "i gotta do it the expensive way, cuz thats the only way". its like the first time someone mentioned using aluminum for a head or even a block. everyone thought "what the hell is this guy thinking, what a dumbass" but nowadays thats the way to go. i'm just saying there are other ways of doing things and they should be explored and stubborn closed minded people should try to understand.