This is a hard one!!! I guess its just because i'm clusterfobic. Not too sure how you can use that space, but i'll answer what i can. Cloth absores light and with that small space you need light everwhere. Get some black and white platic or just seal with caulking and piant the inside white. you can be pretty near to the plant with a floro light, but i'm still trying to wrap my mind around your high issue and remember you are gonna need a planter pot ...... which i'd say min 5" for a flowering plant which is really pushing it with root bundles. I recommend you need to find a growers guide and read up first, lights are 18/6 for veggi and 12/12 for flowering. You might wanna try a lowryder too. happy growing