I need a bigger tank on my Sportster Hugger.

could be under seat or under access panel on left side of bike

You would need a fairing. An old windjammer ro Vetter, or one off a bigger touring bike. There is also a company that makes aftermarket fairings for just about any bike ever made that may be more practical but then you would still need to find the stereo. Cycle sound is about the only manufacturer of motorcycle stereos that I know off. They are hard to come by and expensive. You may also look into a marine grade stereo like is installed on boats. But regular auto stereos and speakers will not hold up long.
A more practical approach would be to put a piece of velcro on your tank and another on the back of an I-pod.

Excess motor oil that blew out the oil cap ,when you've parked for a long time the oil in the tank will drop down in the crankcase,then when you start the motor it will go back in the oil tank and then overflow the oil level...You must have to drain the oil tank again and refill it at the correct oil level....

3 things r needed for starting--r u gitten gas from tank to carb--r u gitten spark--and is compression rite make sure the batt is @12v and cables r tite-inspec plug wires for wear--buy a haynes or clymer manual today

http://www.vtwinmfg.com/Catalog1/VTwinCatalogIndex1.htm

3.3 To 4.0 gal. tanks.

What you describe is normal for a Harley. It's aggravating as hell, but short of swapping the brake system it's an issue you learn to ignore.

look on the left side of the bike back underneath the battery. You'll find a large diameter hose back there with either a plug in it or the hose connects to the frame. It will have one of those spring type hose clamps on it. Take this hose off and drain the oil out of the tank.

Little tip -The only time the oil cooler will cool is when the bike is moving and when the bike is moving you don't need the oil cooler. This is from a factory harley tech.

get a J&P Cycle Catalog. They have the kits in there.

it may be the tank fitting...or the hose or the clamps.