Are there smaller CNG Cylinders (like Santro) available for Alto, so that a bit of space can be created in hud???
you can fit any cyl to the the alto as long as it fits, indeed a smaller one will fit but it'll lmit your range and not really offer much more room.
Any other way to create some room
For Alto a normal cylinder of 40L would give you a mileage of about 70-90km. Santro has three small cylinders of 42L capacity. Check market anyway.
If your car is factory fitted I would suggest you not to change anything.
In Santro we fix 3 x 14wl cylinders, you can fix only one in your car or under the car, then you will have all the space for you.
@LOGASCan you tell the mileage for these 14wl cylinders 1, 2 and three, respectively and combined 2 or three cylinders.