The warm up techniques tent to vary widely, from and extensive 2 hours of warming up and stretching, different type of breath holds to NO warm up.
In general I find the following very important:
Be rested on the day and the days before, avoid stress and exhaution, be warm eat and drink just enough and sleep a lot.
Before the attempt I like to warm up the big muscle groups, including the ones involved in the contractions, I stretch those mildly to prepare them.
I enter the water, with my suit on and my Official Top (OT) time and lane written on my hand.
When possible I have a coach who knows me. He will drag me through the water, time everything, instruct the safety, in short take away any worries so I can focus on relaxation. In the past I used to do warm-up breath holds. I did 1 exhale apnea until the second contraction, and 1 full inhale to a few contractions more, just to put my body in 'dive-mode',while at the same time avoiding wasting my buffers and reserves. You write you're at the 5 minute level, and that may be the time to start to change your static to one with fewer warm up breath-holds. But don't change this 2-3 weeks before your competition.
As of the final preparation I find just floating for 10 minutes on my back breathing very slowly through my nose very relaxing. about 5 minutes before OT I'll do 1 pack-stretch. 2 minutes before OT I'll put on my nose clip. 1,5 minutes before OT I breath a deeper, 1 minute before OT I try to time my final deep exhale, by breathing out in stages, at 25s before OT I start breathing in fairly slowly, at 15 -10 seconds before OT I'll start packing, and when sufficiently full I lift over my right arm over my left shoulder to roll over to start the breath-hold.
This is my current preparation.
At Nordic deep 2007 there was a spleen study that brought up that most people need 3 breath holds to have the body release it's -extra- spleen blood. The effort level of those preparation breath holds is unknown to me, but I suspect one would have to ride some contractions in order to invoke the spleen contraction.
But than I question that the build up muscle fatique and buffers would also be used a bit, and where is the border of benefit?
To me static appears to be very similar to stretching. Everyday 1 good static is much better than one or two long sessions in a week.
I hope these words are of some use to you,
All the best and a happy exploration!
Kars