I personaly look at it this way if you cut the tabs off a 3 tab shingle to use as a starter then you have a 7" starter shingle.
If the landmarks that were used on your house are a metric shingle(5 5/8 tab) then where the two shingles meet you only have 1" 3/8 that the water has to travel up to get to your decking.
Years ago it use to be the rule of thumb that the tabs were to be cut off around here in Indiana, now most roofers just use a whole shingle(me included).
The only time I cut the tabs off to get the tar line at the bottom is if it is in a very high wind area.
The certianteed landmarks are one of the best shingles offered today and will offer you years of great use.
As for going back and changing the starters, you will cause your self more trouble than what it is worth. If your roof has already sealed down and you break that seal removing shinles sometimes they wont reseal, and the roofers are too lazy to hand seal them with tar or silicone.
If I can be of anymore help email me at [email protected], I dont come here very often so I may not catch your reply to my opions
[This message has been edited by SHINGLE MONKEY (edited January 13, 2003).]