can a 55 pound CNG cylinder be fitted in suzuki mehran

a 50 pound can be fitted well easily. l have also searched on this issue, but l find onlyone solution. a 55 ppound cylinder fitting is possible but will have two problem
1) you dont have space to fit filling vlave in bcak hud so filling will be done from valve in bonut
2) back seat holder will be shifted one inch ahead that will make back seat a bit uncomnfortable.
but obviusoly a 55 pound cylinder gives mor emileage with one fill. it keeps about 9.2 kg of Gas.