Two chambers in the same box - you have to make sure that the flowering (top) chamber does not get any light leaked in from the bottom.. This will also mean you need 2 ventilation/exhaust setups, or some crazy creative ducting between them. Plus you will need 2 doors, so that you can keep the flowering chamber closed when/if you want to work on the bottom chamber

Flat white paint rather than aluminium foil anyday - The foil can wrinkle and fold, causing hotspots.

The bottom lamp is a mogul base, so it won't fit in a normal size (medium) socket. It will also need a ballast, capacitor and igniter, since it is an HID lamp.

For the bottom chamber you might consider using regular compact flouros. Much cheaper and decent results if you use enough wattage.

Read through the forums, there is lots of helpful information here and everything you need to know to grow successfully. Good luck and welcome.

Don't forget odor control!