Best ways to transfer points from Amex Membership Rewards Gateway to Aeroplan?

Hi I was wanting to know if there is a way to transfer my American Express Explorer getaway reward points in to Air Canada’s reward program aeroplan. The gateway program and aeroplan program are not linked partners.

Maybe transfer to an Amex explorer partner then in to the aeroplan account ? I just can’t seem to work it out and to get the best amount of points in the end.

The only way I know of is via SPG. You can transfer to them for 2Amex point : 1 point and then from there to Aeroplan. You can also get 5K points  bonus for a 20 K transfer with certain partners. It might be valid with Aeroplan a well so might be worth checking