If you are using a dropshipper, shipping cost would no longer be your concern as this will be shouldered by the customer. Remember that when you list the product, you are supposed to include shipping and handling costs into your final selling price. So in your case if your customer orders two products from two of your suppliers then they will receive two packages in the mail - and may realize that the products they ordered don't come from one supplier.
If you haven't, i would suggest downloading your copy of our Dropshipping Handbook 2010. To download please go to the link below:
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Hope this helps :)
By the way, it would be nice to see a picture of you, if you have a chance to upload one!