Hi there.

Here's a quick shot of my install.
I am using an EMCOTEC RV MINI 5 powerbox and 2 x Longgo 2000mah li-po's. Weight wise this set up is only a couple of ounces heavier than a typical dual switch and regulator/battery combo.
My Extra weighs in at 18lbs but I have a 3W motor and canister which is 1.5lbs heavier than DA50-R with pitts muffler.

Tetly..

Don't cut and shut the can!!!! The 3W is designed to run with the 3W canister and header!!.
My initial set-up used the shorter MTW canister but the motor ran ****e and vibrated quite a bit. It is easy to lengthen the canister tunnel and add extra vents for cooling air to escape. Also you might want to cut some film away under the fuz at the back to allow air to escape from the fuz. The pressure build up otherwise will cause the motor to run rough. I have had all these problems and it's taken me 3 months to sort it out, but oh boy it's worth it. The 3W has more power than the DA-50 and it will hover my 18lb model then pull out with good authority to un-limited vertical. I can e-mail you with more pic's if you want.

Regards James.