Hey Birdwatcher,
Welcome to The Mattress Underground 
! Thanks for your questions. Thanks too for the brief history and lead-in details, they are most helpful and interesting.
Congrats on your new mattress shopping adventure ! Thanks for considering trusted member Sleep On Latex for a possible purchase, I regard their latex expertise, product quality, and customer service highly as they are deeply experienced in the Dunlop latex category. I strongly encourage and support following up directly with SOL on your product questions, either with a phone call or by using the TMU forum (we can let them know that you have unique forum questions for their response if you prefer).
I skipped commenting on points 1 and 2 as they address unavailable products in addition to back-ordered stock. SOL is not unique with supply delays currently. Many suppliers and manufacturers are suffering from ongoing supply chain disruptions globally, as well as soaring costs of materials triggered by scarcity and high consumer demand. You may find this significant price increase post by expert trusted memberMFCinteresting for a more detailed discussion on the matter. In other words, longer delivery lead times will continue to be the norm as long as materials’ availability continues to be an issue.
Until you discuss your DIY options with someone from Sleep On Latex’s team, let’s put your proposed questions on hold for just a bit…unless some helpful consumers may have experience that they can contribute…until then, I’m looking forward to hearing their suggestions for you 
.
Thanks,
Sensei