Determining last blind level

[CazGi]

Hi

I wanna elaborate a blind structure ( <u>WITHOUT ANTES</u> ) for a MTT tournament with T6000 and 200 players, so we have 1.2M chips in play

level duration: 25 minutes

my question is:

how I determine the highest (last) blind level ?

for example:

if I have 1.2M chips in play, do a 30000-60000 level is enough (7.5% of the chip in play before the hands are dealt)

or do I need even higher blind than that ?

some rules-of-thumbs exist ?

Thanks in advance
Caz