compensate shorter bands

Reacently I got a pair of bands for my gabbiano for free, but they are shorter by 2 cm than regular ones for a 100 cm gun. My question is can I compensate this by putting a longer dyneema wishbone ?
thanks

They are 22, I guess it's a 90cm gun band setup. But thanks, I'll just put a 2cm longer wishbone. BTW Spaghetti, do you shorten your bands when they strech after some time of use, or just put a new pair on ?

I didn't mean cut them to make them shorter then recomended for the gun size in order to get some extra punch. But after some time beeing used bands streches and get longer loosing power, for example, after a month or so in the water my regular 20mm bands are no longer 24cm long but 27 or so. Some people recomend cutting them to original lenght ( 24 ), and some say buy a new pair. Along with the gun I bought a few pairs of them and got one as a treat from the salesman. When they passed 28cm in lenght I changed them, but now i have a last pair on and thinking about cutting them to keep their performace rather then buying new ( not so cheap here ). That is what I ment.

Well that depends on numbers of things. First of all the power you want on your gun - more power shorter bands, ofcourse as spaghetti mentioned one can shorten bands only to the certain limit. Also diameter of bands is important when you calculating lenght, for example 16mm have standard strech of 3,3 times, 17,5 - 3,2 times, 19 - 3,0 times of non streched lenght. So first you must messure the lengh between the muzzle and the last notch or shark fin on the shaft - this is a lenght of streched bands. Then you can use the following formula : lenght of the gun ( in your case 75cm ) divided by streching factor ( fd ), multiplied with 2 ( if circular bands ) and add approx. 4cm for the wishbone. So if you want 16mm bands calculation is 75/3,3*2+4= 49. Ofcourse there is much room for experimenting, also diferent brands of bands have diferent characteristics therefore diferent sizes for the similar power. You can find some sizing charts on the web like Rob Allen or Totemsub and by comparring them see that there is no strict formula for every type of band. Above mentioned one is just a frame for experimenting.
I dont no if anny of this helps, or even makes sense, but I use this to calculate bands lenght for my guns and it works fine for me. I would much rather post a link to the article which containes all the basics for bands handling, wrote by Siniša Kekez, but its on croatian so instead I try to translate some parts that seem related to your question.