I use a 7D for photography and have it rigged with an RRS L plate. I want to use the camera for some simple video stuff, and am hoping to use it with a fluid head. Are there any cheap fluid heads that don't come with a QR plate so I can screw on a RRS or Markins plate?

J

You can buy a dovetail plate from RSS that you'd be able to screw onto a normal manfrotto style plate.

Or you can check out my unique solution using parts I already owned:

Fluid head or Ball head? - brian (http://thebeehive.jp/brian/blog/2010/03/21/fluid-head-or-ball-head/)

:)

So I can slap my Markins head right onto a 701 head? How would it attach? I can't tell from the pictures.

You could buy a arca swiss style quick release clamp like this:

Really Right Stuff - Item Listing (http://reallyrightstuff.com/Items.aspx?code=CLAMPS&key=cat)

and screw it onto the manfrotto 701 quck release plate.

In my blog post I describe using a ball head on top of the fluid head, just because I didn't want to pay for a levelling base and another quick release clamp. The ball head just screws onto the quick release plate of the mafrotto fluid head. You can see the quick release plate on the bottom of the ball head in the first picture on my blog post.
Of course, that adds to the weight that I am carrying around every day.
A quick release clamp on the manfrotto plate is the smallest, and lightest solution.

I guess I can't see the 701's screw system well enough to visualize it. I'll have to go check one in person. If I can simply screw my Markins head right onto the 701, I'll be good to go. My tripod is carbon fiber, so weight wouldn't a huge issue. If not, I guess a RRS plate on the 701 works also. What size screw is on the 701?