Go to one of the online MAC (Mean Aerodynamic Chord) calculators (a search here will find at least a couple of my posts on that, giving links), type your wing dimensions in, and read out the wing's (half span's) aerodynamic center. Mark it on your scale wing drawing. The program will give you the MAC and it's position. Then use the rules of thumb that for a flapless model, you want the c.g. at maybe 17% to 20% of the MAC, and for flapped, you want the c.g. between 20% and 25% of the MAC, depending on the ratio of horizontal tail area to wing area. Make the % MAC equal to the percent the tail's area is of the wing's. Those will get you close for a modern proportioned model. The online calculators usually will do that computation for you and therefore position the c.g. for you.
These computations are made according to theory with simplified assumptions that nets useful answers. On line, you don't have to do any of the work. If you want the MAC equations, they're mostly on the internet, or you can get them and their derivations from me. My elliptical wing stuff is better than what I found out there. Anyway, if your model is conventional in configuration, most of the things people tell you will suffice for a start. If not, they will not, especially for higher than average wing sweep. Wing high point of any useful section will not have any significant affect on c.g. position, but as said above, wii affect stalling and thus max lift and drag.
For the leadout position, use the "Line II" or "Line III" freeware. Leadout position can be approximated as 3/4 - 1" behind the c.g. of a "normal" sized model, but it's proportional to size, and depends on line length, model weight, line diameter, speed, air density, etc. Those programs seem to provide a reasonably accurate answer, when used with information from from a site like Palos RC or RC Proving Ground. Do the search or just google these two.
I'm supposed to be doing something else pretty important now, or I'd check out and give you all the answers you need, but I really can't. A search should give you several links. This is important enough that I think you should spend the 5 minutes to 1/2 hour getting a good answer from these sites. 'wish I could help more now, but I'm sorta "outta here."