Gday Chris
I dont know A3S5 well but dont really recommend it for LX90s.
As to training targets, its not height you need, its distance.
If you set up AltAz, set the tripod flat and level, then pick a target as far away as you can on the horizon.
If you are on a wedge, again, pick a target on the horizon and keep the OTA reasonably close to DEC = 0.
Andrew
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