Hi Steve,
I understand why you wanted to change the bolts, but it wasn't necessary. These longer bolts may also be more of a hinderrance than a help.
There is a simple thing to do to the original bolts that is MAGIC in helping one work out the amount and direction of the bolt turning.
The bolt head and the edge of the hole on the OTA are both marked with a little line - this marks point zero. Then when you turn the bolt, you will know exactly by how much and in which direction the bolt was turned, and you don't need to worry about keeping a mental track of this, which when you are also trying to keep control of the collimation process, these marks will free your mind to stay totally focused on the collimation.
,
The diagrams above show a 1/8 turn of the bolt. With the collimation process, you will be doing just 1/8th turns at a time, and even smaller. With an Allen key, this is possible, by hand turning the bolts, you won't have the same degree of fine control. This way you won't experience the star being lost outside of the FOV because you will have fantastic control of the torque and angular movement of the bolt head.
Collimation is also best done using just about the highest magnification the night allows. It is also a misnomer that you make a BIG doughnut with the star for collimation. This is ONLY for course collimation. FINE collimation is achieved using only a SMALL doughnut! It sounds counter intuitive, but man, once it was shown to me I changed the way I collimate my scopes.
Also, if the scope focuses by moving the primary mirror, the scope will typically exhibit some degree of mirror shift. Only a few Cassegrains show no mirror shift with primary mirror focus.
If your scope shows mirror shift, you must only collimate AND focus the scope exclusively in the one direction of turn of the focus knob. Mirror shift WILL alter collimation, and it is impossible to collimate a scope that exhibits mirror shift as moving the mirror inside and outside of focus, the collimation will be stuffed as the mirror shifts from one position to the other.
So, to both collimate AND focus, you need to get into the habit of first turning the focus knob counter-clockwise, and then slowly turn it clockwise.
This will set the primary mirror always into the same position for both collimation, and for best focus.
Now, if your scope has an external focuser, like yours Stephen, then mirror shift won't be an issue (not always though for other reasons that are beyond the scope of this discussion).
Alex.