Cutting it down, in principle, is fine but the lower few feet of the mast usually has the luff groove modified for the gooseneck fitting and to alllow the bolt rope to enter. You will have to check this will be OK
If 1.1 metres removes all the fittings, sail entry, halyard exits etc from the bottom it sounds a sensible way forward.
Otherwise unless the mast is tapered it might be less work to cut the top off!
Whichever, the crosstrees and lower shrouds will have to be repositioned.
You need to look at the new mast in terms of fittings that will need to be moved. It is best if you can avoid moving things leaving holes.
So I would guess that the spreaders might best be left in place. That would mean cutting off both the top and the bottom. But then that assumes you can easily reconfigure the top for halyards and the bottom for halyard exits. Re exits I have settled on having exit slots for the halyards in the side of the mast rather than turning blocks at the bottom. They need to be something like a metre above deck and for wires you may need a little ss plate to stop the wire cutting the mast.Make sure however that the halyards exit at different levels and points on the mast to avoid making a weak point.
Regarding the top of the mast. If it has a crane and built in sheaves you might think this the best part to not change. In which case move the spreaders.
The slot for entry of the bolt rope or slugs in the mast track can be easily cut out or in some cases opened up. I have always cut it out. I cut with a hacksaw where it ends then use some multigrip pliers to bend/fatigue the metal until it breaks.
good luck olewill
I adapted a Dragon mast to fit a Hurley 19. The mast was tapered and I wanted the lighter bit at the top, so cut off the bottom. It's easy enough to make an exit point for an internal halyard. I opened the luff grove with a screwdriver and pliers.
In the middle of the mast may be a big flat bit of aluminium, so placed as to allow the mast to bend fore and aft, but not sideways. I simply removed the whole thing to save a little weight.
You need to make sure you use the right rivets / bolts to not cause electrolytic corrosion - forget what they're called.
This would only apply if the mast was tapered , the majority of masts are uniform thickness throughout .
I have "adjusted " my mast ( 3.6 mm wall ) and cut it with a hardpoint saw then cleaned up the cut with a 300mm sanding board . If you have one big enough , a chop saw would be best with a 72 tooth tungsten blade .