Vegas Masking? opacity? Need help please

[William James Ryan]

Im working on a project where basically I'm chasing myself up some stairs, and I'm wondering what the best way to go about mixing the two clips together would be. I've had my arm cross over myself before, and walked behind myself, but those were only moments and even then I could see little "i dont know what Im doing" blurry lines.

Here's a clip at half opacity to show you what Im looking at.

Thanks in advance for any advice

**the clip is too big @ 1.25 mb. sorry. i dont know that the veg file will help