XTRA Large Growbox - Australian Made - Pics to Come

Hi everyone,
first post but long time reader of these forums. I have recently contructed my very first grow box, now i have a few questions but a bit more about that later, first i will just list the things i have done.'

I started off buying 3 black plastic grow boxes that measure 1.4m x 80 cm by 60 cm high. (4 f x 2.5 f x 2f high), additionally i bought a 20cm ventilation fan that they use in vanities and walls (8 inches), then i bought myself some 10cm (4inch) pvc pipe for my passive intake, i also bough two right angle connectors to minimize light entering into the box. for light i have 1 400 watt HPS with ballast.

Construction ( PICS TO COME, i will post up asap, i have drawn one as camera is only being returned to me in a few days)
- I soldered a hole for the fan in the top box and mounted it in the side.
- Then i mounted the fan in the box
-Cut out the bottom of the middle box so it was just the shell.
-i then lined the inside of the two lower boxes with alfoil, you may call it tinfoil?
- i then cut holes for the intake in the bottom corner of the lowest box and made sure it was all airtight, the intake runs along the box then turns at a right angle along the next wall of the box
-After doing so i mounted the 400 watts HPS is the top box (it is fixes so it cannot move but i can always change this if needed)
-This is basically it took me around 5 hours
the box is currently standing at 5 feet tall.

http://i33.tinypic.com/iljcef.jpg

Questions
1) The temperature in the box is at a constant 30 - 31 degrees Celsius ( 86- 87 F) is this to high,it is about 8 c higher than the outside temps. i have the fan running constantly with the HPS. If it is to high can i simply add another 'storey' to the grow box to make it four boxes high.
2) Is the ventialtion adequate?
3) Do i need an additional fan insdie the grow box to promote strengthened stems or is it enough?
4) Should i be using different lights for the veg and flowering or can i use the 400 watt hps thorugh out and switch to 12/12 when flowering.


Notes -
- Keep in mind my budget is almoast all but run out, i am not after the biggest and best yields money can buy, just a good yeild that will last.
-I know this seems alot of questions but i have read thorugh all the stickies on this site and others and i have been researching for a while i just want to get this grow under my belt as best i can.
- thanks for looking and any advise you may give me!
Unispanman

I would get rid of the tin foil and paint everything flat white. 87 is about 5 too many, but will probably grow weed. You need to vent your grow as well as your light. Blue light for veg, red for flower. 5700K and 2700K respectively.

ok, i will get rid of the tinfoil asap, another question is the HPS light to close to the plants because the soil seems to get really hot and dry inside there, also what would be a way to reduce the temperature inside?