I don't know much about bmx frames, i'm yet to get my first bmx actually, still waiting......but have always likes the simple enigma frame and the specs seem to match up to your wants: 20.55", 20.8" or 21.05” toptube. 345.85-364.70mm/ 13.62-14.36“ chainstays. 74.5° headtube. 71° seattube. Full 4130 cr-mo, heattreated, Sanko Japanese tubing. Double butted top and down tubes. BB Height 35mm/ 138" // Spanish BB. Integrated headset. Removable gyro tabs. 5mm lasercut and heattreated dropouts, CNC'd on the inside. Extra large blowholes for reduced weight. Slotted cable guide for easy brake removal. 2.25kg/ 5.14lb.