Re: the mast or spar kit...
Dwyer will help you out with the spars if you send them the sail plan. They have been doing this a long time. They might even have an AR15 sail plan on file. They know who Bateau and Jacques are (is?) .

Depending on who you speak with, their first responses or explanations may not compute on your end. Just ask them to say it again differently, so you are both on the same page. And then feel free to relay any continued confusions (if any) here. Or call Jacques if you find it difficult to put into type, but try the forum first so we can all benefit from the discusiion and resolution.

I don't know what I'm talking about. I'm still getting the feel of sailing with sea trials. I'm not even up to a *wise-fool* yet, but others here have 20 times or more the experience I have. The trick sometimes is hearing an answer in a way that *you* understand to *your* satisfaction, when you need that satisfaction to help bolster simple trust.
About the light vs heavy build...
The longer version...
F=MA
Force = Mass x Acceleration
In that relationship, if the mass of the boat is half that of an overbuilt version, then an equal amount of force from the wind will give you twice the acceleration, theoretically, but there's also drag and sail trim and other issues. But, at half the weight, though you have less inertia to overcome to get you going, you also have less momentum once going. If you are barely moving compared to your *not moving* competitor, that's good. But in light puffs, if the heavier boat plays those puffs right, he might accomplish a tack to windward successfully because his momentum of that extra mass carries him through the maneuver, whereas you might get stuck in irons or need to bear away before the tack to gain speed for the maneuver.
Light air racing requires its own skill set, including a good understanding of where the next puff or wind curtain is most likely to occur. But all skills being equally proficient for light air, the lighter boat is more likely to cross the line first. This seems like a petty parsing of words...

but I would say that it is not quite that the lighter boat handles better, but that the lighter boat has the potential to perform better with the proper handling by the skipper and crew.

A lighter boat, in some instances, may require more skill to handle well.

Same for a heavier boat, just those instances are different.
If the class of boats can plane, then when the wind kicks up, once again the lighter boat can benefit from more acceleration in gusts, getting the boat to plane for awhile, where the heavier boat might not ever plane if the wind isn't strong enough. So if the skipper and crew are sharp, the lighter boat, that can plane, may plane in short bursts where the heavier boat won't. If the wind is steady and strong, the lighter boat may still plane for longer periods, but may slam to a stop more in a chop. Overall, the greater time planing, I think, will make up for the more possible sudden stop. If the heavier boat doesn't plow through the chop, but also slams to a stop, he will accelerate slower from that stop.
If the boats are displacement and need a jet turbine to get them to plane, and the wind is steady, things are markedly different. For then the benefit of less weight begins to drop except in that the lighter hull can put more weight in the bulb or board and carry more sail. In a class with strict restrictions on bulb weight (which is being debated now), or on sail area flown, it becomes wiser to build a stronger boat if lighter still won't let you put more in the bulb or fly more sail. Sail trim and boat trim and tactics and a good weather eye and a clean and well faired bottom become more important than just a few pounds of weight.
With an AR15 you will probably race within all sorts of fleets since there is no established AR15 fleet. There will be some sort of handicapping system to position you fairly among dissimilar designs. If you can get your boat to plane, and you are not facing a four foot steep chop (

), then light is the way to go, okoume, maybe meranti on the bottom if you want that a bit stronger (and it keeps the weight low which is good). When plenty strong for the worst expected conditions, light will have more advantages, but the skipper and crew need to know and work those advantages or they may still be beat by heavier boats.
If you build a little heavier than an experienced builder, and don't build an outright pig (like I did first time (but is nuke hardened

)), (and she's a lovely pig and sails well), then you're gonna have a lot of fun learning those subtle and not so subtle details.

There, I typed way too much for today....