I don't believe in putting lotus deep at all.
All they need is a few inches over their crowns.
The lotus I have in the big pond is Mrs. Perry D. Slocum and it is a HUGE sized lotus,
so the deep water doesn't bother it at all.
Plus it is not potted, it is planted in the mud....filled up the pond in 2 years.
So keep yours potted, unless you want your pond to be all lotus in 2 years or less.