I'm quite sure Ian can build you in-wall M60s. They'll likely give you 10Hz lower extension than on-walls.
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BANNED & QUARANTINED
A-LFR/1000-8 & 2/500v4x2
1000-3,1500-3
100,160,QS10x2,800,M5x2,M2/3/50v4
had v2