While attaching board to roof racks the other day I broke a strap. It was a cheap soft rack.
Luckily I could just get the strap to reach when I flipped and spun the board to a thinner part, but only just. Would have been a bitch to get home if I couldn't, I'd also left my mobile behind on purpose, to get disconnected. Actually it would have been impossible to get it home.
What other things should I carry spares of? I'll start a list:
- roof rack straps
- mast base tendon thingy
Tendon, yep
Harness lines
Downhaul rope
Sail tape
Foot strap screws
Vent plug O-ring
And beer 
Also a few basic tools to fix the inevitable breakages so
* screwdrivers
* Pliers
* shacklekey
* matches
my spares.
extension, uni, base plate, 5m sownhaul rope, metric fin screws, imperial fin screws, us fin screws, fin tab repair kit, fin nuts, stainless steel washers and neoprene washers, multigrips, side cutters, pliers, stainless steel bolts and nuts, file, screwdrivers, allan key sets imperial and metric, socket set, stanley knife, shackles, mast cap, boom arm twist locks, rivet gun, rivets, mylar repair tape, duct tape, batteries, wet and dry, heavy sand paper, epoxy repair kit, harness lines, fins, silicon spray, garden hose, helmet, winch, hydropuller, radiator hose rings, first aid kit, mast plug, mast tip adjusters.....
well that's off the top of my head.
probably other stuff floating around in there. basically i salvage all trashed stuff and add it to the kit as spares.
it's surprising how often i help someone out or use the kit myself.
Couple of screws one gauge bigger then your footstrap screw for when they pull out and you can't find a stick or match to bung in there
Some shirtbox plastic for shimming fins if you have a US box
Fin bolts
Sunscreen for when you forget (bummer if it is a full on day and nobody has any 
)
BTW your downhaul would have been long enough to strap the board on? If you use softracks all the time I suggest real racks. I get nervous having $5000 on real racks with 2 sets of straps..... I'd never use softracks except if desperate and no more than 80kph for 10-15min
well greenroom, once the son of auto electrician, always got to have the right tool.
mark, mast tip adjuster is for the older style sails, like the norths etc. they had a plastic pin that was held in place with a piece of webbing.
the plastic pin then seated in the top of the mast. some mast brands were too small and others were too big, so i had some different sized pins and some adjusters for the top of the mast.
Ahhh so you menat adapter
My Simmers are the same but I did away with all the pin type things on the sail head and replaced them with Fiberspar cups so any mast slides into the sail head strap.
)
Damn lucky we didn't kill someone. 
4m of downhaul rope - tied to end of boom.
bit of bacon saving insurance for following ..... 3km's from the shore
downhaul
outhaul
fix uinveral joint
fix harness
fix boom clamp
tow home
hold gear together if you have to paddle
use it as an uphaul rope
Gestalt, i'm just waiting for the day you show up at the beach with all that emergency stuff - and realise you've forgotten your board...
that's a good one...
well i forgot my mast last weekend, had to go home.
although it sounds like a lot of spare kit it all fits in 2 plastic tubs.
Damn lucky we didn't kill someone.
Damn lucky we didn't kill someone. 
