I havent had any problem with the small tarp hooked to the hammock. it does drop down on the ridge line, but i figured that's what the ridge line was for, in addition to holding up the mosquito net. I've tried it both ways.
The advantage to a separate ridge line is: if it's raining you can get the tarp up first, then worry about the hammock. And, if you are taking stuff down the tarp can come off last, after everything else is safely packed.
My feet keep getting wet in the rain. I can't figure out why or where it's running in on me. The tarp I have been using has been centered, but the outside of my bag keeps getting damp. Next trip Im trying my hex tarp. I could sleep a family of four under that thing and stay dry.