For lights I use Imageclip for inkjet which is a two step process transfer. The polymer is removed before the transfer is pressed on the shirt. It does require a B/W laser toner printed plain paper mask for removing the unprinted polymer. The mask can either be printed directly with laser printer or a copy of inkjet printed mask using a laser copier that is available at any copy depot.
Here is a link about Imageclip for inkjet:
How Imageclip for inkjet test - T-Shirt Forums
When I use laser or inkjet transfer that leaves a polymer window I mask the unwanted polymer with a plain printer paper that I cutout the image part. I then place the rest of the paper over the transfer paper. Trim the edges that are over hanging the mask. Press the two papers covered with parchment paper for 6 seconds at 225F with light pressure. Then press the combo on the shirt using recommended settings for pressing the transfer paper used. The plain paper will prevent the unprinted polymer from transferring on the shirt. By using a cutout mask you don't have to worry about placement issue when the image is/are in separate pieces.
Here is a link for masking:
what is considered light colored shirts? - T-Shirt Forums
I seldom use opaque transfer. When I do I use blue grid opaque. It has to be trimmed to remove unwanted opaque material if the image is not rectangular. A vinyl cutter is the best tool for trimming.
Lights and darks question 
CorelDRAW macro author
