[pct-l] silnylon questions

[mardav at charter.net (Marion Davison)]

I have a large inexpensive tent that I really like, except that we get 
water leakage through the floor when it rains.  I am thinking about 
replacing the floor fabric with silnylon. We aren't intimidated by 
sewing; we have made tents, sleeping bags, packs and down jackets.
 I have questions for the experts.
1.  Would replacing this floor with silnylon probably solve my problem?
2.  Does silnylon come in different weights?  What is the best weight 
for a tent floor?
3.  Are there any sewing tricks I need to know to successfully sew silnylon?
4.  Can you recommend any suppliers of silnylon?
Marion Davison