I guess Marstroem was and is quite busy to produce the Extreme 40, Seacart 30, Tornados and spars for Beijing, recently build Roman Patzkes 90 foot G-cat and there might still be some aerogliders on order too... so could assume their autoclave is quite booked for some time... :-)
but he is not the only builder you have to beg and please to get what you would like...

also agree too many A mast break for to little reasons but it has not so much to do with weight as I haven't heard that the spars got lighter over the years. they became softer, prebend increased, diamonds and shrouds were lowered, sometimes fiitings were bad manufactured etc... there are a few knowledgeable people saying it would be possible to build a 6-7 kg light A mast but it would not survive certain capsizes. anyhow mastbuilders could increase the durability of their masts with some not to expensive additions and my only explanation so far is, they don't do it because neither the sailors (as client) demand unbreakable masts (they should do so so!) nor does a consumer have enough consumer rights in a not so much professional and commercial environment to ask for a new mast once the old broke. I believe mastbuilders do not care to much also as broken mast mean new masts which means ongoing business. the only positive effect is that broken carbon masts offer possibilities for the low budget 2nd hand market. but the durability of a mast depends on it load patterns and detail solutions and just a minimum weight restriction would not solve the problem. and 4 kg is nearly 50% more heavy (for a 6% shorter mast on a 11% shorter boat) than some A masts do weight which survived more than 10 years. In general I have some doubts that adding weight is the smartest way to go to increase the durability of catamarans although the weighty F18 class seems to be bulletproof nowadays... but they say this also about tanks and I don't think tanks sail well.