Tz7, not to be a party pooper, but you are simply trying to use the wrong tool for the wrong job.
SET amps are primarily designed to drive high(er) efficiency, high(er) impedence, relatively stable speaker loads. I don't think Magnepans meet any of these three criterion. And Zero's will only address one of these issues. But, it might be worth asking the Zero's maker, Paul Speltz, he says that over half his customers are Maggie owners. Perhaps he knows of some amps that work.
One thing for sure, there are very, very, few SET amps intentionally designed to deliver high current. And they are damned expensive. But even then, I'd guess the current intended for most 90-100dB speakers is entirely different from what your speakers want. Not even in the ballpark.
I own one of the few brands of SET specifically designed to deliver high current(for SET), Art Audio
. They make a 50wpc "high power option" Art Audio Jota BX
(using the KR 52BX tube) that has both 4 & 8 ohm outputs. It "employs larger transformers and adjusted internal parts values to support the increased demands and current delivery". But, it's going to cost you $10k+
If you are really serious, AA makes Jota monoblocks that can be made in the high power option. It'll cost you north of $15k, but if you are really serious about Maggies and SET, are probably the best option.
But, all this is seriously unrealistic considering your speakers only cost $1,100 brand spanking new. Nor is SET the the way to get the best sound from your Maggies.
Although.... I think Single-End Pentode (SEP) amps actually work better the lower the impedance they work into. And there are some great, affordable, SEP amps being made right now. Don't know of any above 9wpc off hand and have no idea if they will drive Maggies.