Mellotronists

Maybe the person wants to know the correct length in 
inches/centimeters...and the amount of tape ahead of the beginning of 
the sound, and after the end & the proper length to clip...assuming 
maybe the person wants to mail spooled continuous tapes or ??? A 
silly Q at first observation, but maybe there's something deeper. 
More details on the request, please.

I'd take the lid off mine, but currently that means removing 
everything off the top of the last flat space in my cluttered abode. 
A very major undertaking.