Foil is a poor reflector of light, try get your hands on some mylar. It is relatively inexpensive and is easy to find. Also, flat white paint may be used. Bothe are better than foil.
In regards to the veg period;
This is absolutely under your control. you should ideally veg until you have a decent amount of nodular development.
Other considerations for period of veg cycle:
Plant size. In most cases the longer you veg, the larger your plant is going to want to grow. For a stealth grow, you may wish to keep the plants on the smaller end.
Hope that helps, somewhat!
Happy growing!