Like you I have odd genetics. I get thick as fuck in the chest and back, but have a hell of a time growing my limbs (legs included). Over the last several years I have tried every routine I could get my hands on and oddly what works for me is;
Legs 2 times a week. High reps and high sets.
Arms indirectly 2X a week and directly every other week. On direct days only 3 exercises for bis and 3 for tri no more than 4 sets for bis and 4 sets for tris.
I know, this is extremely odd. I doubt this will work for you.....here is my point;
I have kept detailed logs (spreadsheets) that track everything from my diet, routines, blasts to my blood work, body measurements and supplments. After years of trial and error this is what I have found that works for me... You have to find what works for you. This best way to do this is to track everything.
Every Sunday I wake up take a piss, then go to exactly the same spot, with the same lighting and take a picture face, sideways and with my back to the camera; I then measure every part of my body. I do this fasted and on the second day of my days off, this way I can not confuse pump with growth.
*** I see guys saying you can't over train on gear. This maybe the case for some. This is not the case for me. I blast and cruise. If I don't take a week off every now and then I literally see my lifts go down, I start getting injuries and sick. Another thing is see is plateaus. These plateaus are obvious when I over train certian muscle groups......legs and arms for me.