Tipping installers?

Hi, I am working with an interior designer who takes a 30% design fee on all the sourced furnishings. We purchased some shades through her, and she also arranged for the install of 6 shades. The price of the install was included in the overall fee that we paid in advance to the designer (she did not apply a design fee to the installer's services). I didn't tip, because I he did a lot of work (2... [more]

Hi, I am working with an interior designer who takes a 30% design fee on all the sourced furnishings. We purchased some shades through her, and she also arranged for the install of 6 shades. The price of the install was included in the overall fee that we paid in advance to the designer (she did not apply a design fee to the installer's services). I didn't tip, because I he did a lot of work (2 of which involved very high indoor windows). The installer had one guy help him for two of the windows, but otherwise did everything else. What is customary practice in this situation and when you are working with persons who are hired by your designer? If it is customary to tip, how much would be appropriate, and because I didn't tip, would it be good to follow up with a short thank-you note and small gift card? Thanks for any and all input! [less]