Supplier funded stands ought to be used to promote products from that supplier.
Using a supplier stand to promote products from another supplier disrespects the relationship.
In one newsagency I saw recently half the double-sided stand was being used to promote competitor products. The risk is the supplier removes a useful stand.
I no longer use their stands (woolworths actually gave me a really good one) If one magazine compliments another i do not see why not do it ,increased sales is what we are after and besides that i have never heard from a magazine supplier unless they are chasing money .
Also you need a relationship to be able to disrespect it ,what we have with these 2 companies is hardly a respectful relationship .