i would do it, xfi. when i did my car, there was a slight upslope to the rear tray just from the way things were laid out. so it would make sense to keep that upslope going right on past the bumper if you're ok with how it looks.
i may do something similar when i do my permanent version.
but i haven't played with my undertray since last week's aborted test. i've been preoccupied with the forkenswift lately. i'll try again in the next week or so for another comparison run.
You know what I'd do with a Rabbit pickup? Aeromod that thing to hell like Phil Knox's truck, install LRR tires, synthetic transmission oil, adjust to a 0/0/0 alignment, correct all brake drag, load the *** end up with 2,500 pounds of flooded lead acid batteries, install an 11" Kostov motor and Zilla 1k. Basically, for $8-10k, you could make a 150-200 mile range electric truck that tops 110 mph and does 0-60 mph in 16 seconds(slow, but able to hold its own against a Diesel VW Rabbit), 0-30 mph like a Ferrari(fun for around town in this regard, blow off Corvettes. Just hope you scare them off so they don't blow your doors off when you run out of go after 2-3 seconds of tire smoking. Add more expensive sealed batteries and Zilla 2k if you really do want it to keep on pulling, which adds $5,000+ to the cost). And you wouldn't have even touched advanced batteries or weird voodoo AC motors and **** like that.
To make a 20 mile range 30 mph commuter out of it would be a waste of a perfectly good truck. So much potential. Similar trucks have been made without aeromods, and have gotten 100 miles range at 60 mph, 80 mph top speed, for roughly $8-10k. So the next logical extension for maximizing range and top speed is to make the design more efficient, and I don't know anyone that's tried a severe body makeover for drag reduction. Reducing drag coefficient from .45 to .25 would theoretically double the range! In practice, it might be more around 50% more. Who knows.
If I had the cash and wasn't tied to my current project, I'd try it!
Finished the rear tray. It sticks out the back about 5". The way I installed it (so it wouldn't 'scoop' air) is flat. No angle up at all.
Thinking about finding a rear bumper cover from a swift gt (still trying to get some reasonable shipping from the one I found) and relocating my license plate upward inbetween the lights. Then cutting the rear bumper cover and angle the coroplast upward. Don't want to hack up this one, the license plate would be in the way anyway.
On another note-purchased a rear hatch from a 'U PULL IT' yard. Happens to be white (and off an XFi) to match my car. Removed the rear glass from it then stopped by a custom marine upholstery shop. I explained to him I would like a 'canvas' rear cover and zip out window in the back. Scheduled an appt for the week of May 8th. I figure this will lighten my vehicle and provide excellent flow through ventilation in the summer.(NO A/C). He even has white material to match the car...Nice guy...didn't laugh to much at the request.