How safe is to do scrapebox blast to 3 years old site?

Hi,
I have a quick question ...
How safe is to do massive scrapebox blast to domain which will use 301 redirect to my main website?
The other domain is hosted in different country. My main site is 3 years old + pr5, the main site is update daily by adding news and other information as well.

Thanks in advance!

P.S . Any other suggestion to get a better ranking are welcome...