Sorry to bring bonding up again. I read and I read but not having two DSLs in the same location its difficult for me to test this.
I have a customer with a UK 80/20 FTTC connection where the upload speed is restrictive for the data they need to send. The solution is a l2tp vpn with EoIP bridge to my x86 Mikrotik which is vlaned at my end and then presented to a single port on a switch internally.
I was trying to work out if I could bond two DSL's on the customers 850GX2 back to my x86 router and get 2 x 20 upload. I realise its not the best solution but cost wise and no FTTP its the only solution for that site.