Check the Class Rules (on this site,  Members’ Area)  but from memory all aspects of the design of the pole apart from the length are optional,  and  –  again from memory  –  I am fairly sure that the maximum permitted length is six feet   That length will of course have long since been metricated,  so what appears in the Class Rules will be the metric equivalent,  which is why this dimension (and indeed all the others) are awkward numbers of millimetres.

As to your question “Will it work”,  the crucial considerations are weight and strength,  and if you are cutting down a larger pole it may be unduly heavy.    If too heavy,  it may tend to unduly pull the sail downwards in lighter winds if the uphaul permits it to droop;    using an all-rope uphaul with no elastic in it should help to address this issue.   If not strong enough,  which is less likely to be an issue if you are cutting down a larger pole,  there is a risk of buckling in stronger winds.

In the absence of information I presume that this is aluminium alloy,  and designed as a spinnaker pole,  so both the material and the wall thickness are likely to be suitable.   But early GP14 spinnaker poles were quite commonly made of wood,  and I have also known (older) alloy ones that were too light for the maximum loads they can carry.   The modern GP14 spinnaker p0le is a well engineered tapered alloy pole,  which combines adequate strength with the avoidance of undue weight.

But since you have already picked up this larger one,  the best advice may be to shorten it to the required length and then try it and see.    There is a good likelihood that it will work,  although it may well be heavier than needed.

Oliver