in 2e, base beholders had a fly speed of 3(B) - which was good maneouverability at 30’ round… as you might imagine, i based all of my monster designs on 2e 🙂
in play, i always figured that given a beholder’s natural buoyancy and nonmagical levitation, any other magical movement effect would be ADDITIVE to their natural movement rate - so, for example, they could get a little speed bump to 40’ round using their telekinesis beam as a bonus thruster…
