sorry, but aluminum is almost 200 times stronger than tin, and has a high weight to strenth ratio. thats kinda why they use it to make . Usually it is used as a coating on aluminum, iron, copper or steel to prevent rust. mostly it is used as a conductor in electronics and such. it IS however more easily bent than aluminum or aluminum aloy's.
abou tsewing your armor to the vest. what kind of thread are you using? did you get some good upostry thred? i dont knwo of any thread short of rope or leather that will hold armor plates or armor with edges for a long time without cutting itself in half. i propose the following:
once youve finished your armor, dril or punch holes (shodul be extreamly easy with tin) at two to three corners of the armor. use a flush mounted screw and bolt directly to the vest. once tightened all the way, use JB Weld to secre the nut onto the bolt so i till not vibrate or jar loose. Bondo over the hole and spot prime, andthan paint away! and POOF!
you can use INDRUSTRIL velcro only on teh armor plating. this will NOT come loose in the heat of battle. the only issue is you might either want to hand sew the velcro to the vest with an upolsters needle (thick one) or use the proper needle in a sweing machine and go slowly.
both ways work perfect. the blot way will NEVER faitl, however, the velcro way will not fail in 99% of cases studied.