Its overkill to add more senses in (including taste and smell) and heres why. As you have discovered when doing SSILD it is very quick to take hold and produces lapses in consciousness sometimes from the very first cycle. To add other senses in then you may not get through the 'required' 4 cycles before falling asleep. I find that seeing, hearing & touch are powerful enough to bring into the dream state

Although SSILD is unknown why it works, i believe it is due to becoming aware of those senses and so when dreaming you are more aware of the dreamstate hence increasing the chance of spotting oddities and becoming lucid

However, there is room for manipulation during SSILD as you can add in other techniques. During the 'hearing' step I like to say a MILD affirmation 'I become aware in my dreams' or during the 'seeing' step you could visualize a dream scene for a few seconds.

Remeber though that SSILD should be done really dumblike - the trick is to fall asleep during the cycles or soon after it - and watch out for those false awakenings!

Ezzo