That 105-107" measurement is from the bridle tang located on the hull near the bow ... to ... the mark measured up the mast .... it does not involve the sidestays/shrouds.
You may wish to goto the "Hobie Forum" ... look for TheMightyHobie18/h18SX ... there is alot of information there as we constantly re-post information ....
Harry
H18Mag/P19MX