How does VPN trunking work with regard to bandwidth\sessions?

If I link from one location to another using 2 vpn connections and trunking can a single session use VPN1 + VPN2 bandwidth? or can the one session only use a maximum of one VPN link?

I'm thinking of using VPN trunking as a DIY DSL bonding attempt. Thought maybe I could use 2 DSL lines from my location to another property that has fiber to maybe get me a faster internet connection. I know it's complicated and setup will be expensive (already have a 2955, so I need 1 more) but could\would it work?

any thoughts gratefully received.

drewy