I have a 30G still waiting to get built for the same reason. I have all the parts for it and like you said, it feels heavier than my 55. My 55 has three 3/4" intakes, one on a riser w/ball valve and I have no issues getting it up to temp (usually 250° or so) and keeping it there with 1 nipple uncapped and the ball valve 1/2 open. I plan on using the same setup for the 30. As far as the dome lid that you want to do, you'll need to find an 18.5" lid. That will be the closest you'll get. I ended up buying one direct from Weber since I couldn't fine one on CL. My plan is to do the same thing I did to my 55 which has worked great for 2 seasons now. I got a video of my Weber lid setup (and build) on my YT channel below. Good luck with your build. I'm going to try and get mine built here sometime before summer, but it's not looking good with other commitments.