brinked - 6:49 am on Apr 19, 2012 (gmt 0)
interlinking probably isnt a good idea in that case. It all really depends as well. Most of my experiences dealt with websites that had very little unique quality content so I dont know how that factors in too well.
Its just not worth it. It's best to have them on separate servers, different whois etc..its not that hard to set up and you get to rule out one possibility for a penalty.