Questions about posture during sitting

[LotusBud]

This may be in the wrong thread area so mods feel free to move .
Hello all.  First post here so sorry if the answers were somewhere already stated. 

1) When meditating, I find my posture starts to collapse as I get deeper into relaxation. Head drops and back slumps forward. I am wondering how to correct it without ruining the depth I may be achieving in that moment.  I have been slowly righting myself with each breath as if inflating myself back up like a balloon as I inhale and exhale without  trying to give it much thought.  Is this correct? or is there another technique I should be employing or should I stay put? 

2) Also I am wondering how slow should my breath get when at the deepest state?  I could go slower,  but I am wondering how many seconds some of the experienced practitioners here take for a full inhalation and exhalation. 

3) Also I am putting my tongue on the roof of my mouth behind front teeth. Is this correct? 

4) And finally where should my eyes be positioned behind my lids. I am sort of looking or imagining looking at my nose trying to focus on the air going in and out.  I find my eyes can wonder a little sometimes from right side to left.  If staring in one direction will it activate one hemisphere of the brain more than the other?  I thought one hemisphere is more attached to emotions and the other more attached to logic, reason, and numbers. Is there a way to trigger less thoughts?  Anything to this?

Thank you and kindest regards
phil

[Vivek]

Can you please first check the info posted here: http://www.vipassanaforum.net/forum/index.php/topic,2047.0.html

Some of the information should prove helpful.

[LotusBud]

Understood.

Thank you