Comment by muzani

There's a trap to be careful of here, because your estimate now is 1.5 months, so it's actually going to take 3 months.

The general rule is 80% of the work takes 80% of the time, and the remaining 20% takes 80% of the time. Try to get 80% of it done in 50% of the time.

So the goal should be to get development 80% done in 3 weeks and begin QA by then.