Can Demands/Supplies be accumulated at start of the month instead of end

Summary:

We are using Constrained plan. So, we can limit our time buckets for 150.
Plan horizon is setup for 1 year out of which 60 in Day bucket and 10 in Month/Period bucket due to performance issues. 90 days and 9-month plan is too slow for our dataset

Some of the items which has lead time of 90 days. Incase if demands are created at 61st day, that will be end dated at Month end and supplies will be fulfilled at 90th day if no enforce purchasing lead time is setup also. This causes the demand to be fulfilled late by 29 days. We also have items of lead time for 5 months.