I have a manual from the K3 Master System bought here in the UK.
There is a "Tip" at the foot of page 7, which is the Quick-Start Guide, about setting the Depth Collar closer or further from the Shoulder of the Drill Bit. It may be that if you set the Collar nearer to the Shoulder, the shallower hole may allow you to use the standard 1 1/4" screw rather than having to buy the 1", unless of course you already have the smaller size.
Perhaps try on some scrap to find out how much closer the collar has to be set.
Hope this helps.
...Such stuff as dreams are made on.