Axel placement in new frame

Hey folks , hope you all had a great Holliday. Now the question. After reading and doing a bit of homework it looks like the axel placement on the frame is about 36-38% of the total frame length???? So if the frame is 120" long you would place the axel at aprox 76-78 inches back? Does this sound correct? I'll be welding the frame this weekend and wanted the Pro's opinion. Thanks for the help. Happy Trails