Setting the Rowlock in car bog should work I imagine
The stiffener in the base of the mast is a trade off of stiffness versus weight
versus cost etc You want the stiffest you can get without too much of the other factors
Your call 
One of mine is wood with a layer or two of carbon at the very bottom
I'm going to try the car bog idear i think i will get the rowlock closer to the centre with this method,what i planned was to cut a disc of foam rubber(may a sponge)and fix it to the end of the rowlock and insert it into the boom stand it up verticle and pour in the bog the foam/sponge will stop the bog running down the boom then wrap a piece of gal wire to the rowlock locate the position i want then let set.
If the bog shrinks and i can pull the plug out after it cures i will score it with a file then cover it with liquid nails re insert it then screw on the pulley mount to secure it.
Or dont use a rowlock at all I tried it once and havent bothered since
If the pulleys are in the right place a rowlock [or gooseneck] is hardly necessary
Thanks for input hiko/test pilot now i have to make a call ,i have the rowlock but do i need it ? i think i will test boom against the mast and pre rigg the setup and position the boom pulley so when its hauled down the boom dosn't hit the mast ,what do you think
I have decided to stick to the plans and use the row lock and tried the bog idear and it seems to have worked well have a look.
I Fixed a sponge to the end of the row lock then inserted into the boom
Then filled the hole with bog then adjusted the row lock into the correct position held it steady for about a minute untill the bog started to go thick
Cleanded it up gave it a little black paint then screwed on the block and saddle.
Then drilled the holes and V lock for the outhaul cord.
If you can't turn down a piece of wood to fit as a plug for your boom you might want to try this option very easy (Tip wrap some paper or cloth around boom end and tape it the bog method is a little messy
Hi the sail is finished and so i thought i would fit it to the yaght witch is nearly finished just need to paint the GT stripes on the seat base took a few picks not very good ones but i will post them any way
I will need to extend the mast by about 6 inches witch was cut from the mast when i bought it
I cant sheet the sail in properly because the blocks are to close together
All i want do do is go for a ride can't wait
If you put a small extension on the top of the mast you will then be able to sheet in further/tighter.
You are guarenteed to have a ton of fun with it.