A couple of comments after seeing your video....the optimum placement for the girder really can't be determined until your under the house visually seeing the condition, so the 9' reference unless he went under and spent some time was a + or - estimate.
Typically, center of the span is optimum but load bearing walls above could offset the load point to off center..Regarding the 1/4" space, not uncommon, the bottom plane of the floor joists will not be consistent with the straight plane of the girder, hardwood shims should be installed , we then secure the shims with construction adhesive..
Just another insight into this type of work. Laying on your back, and crawling around a 3' crawl space with a dirt floor for most people is not much fun. Spiders, garbage, and other unpleasant things make it a job that most people want to get done ASAP..
In my early 20s I learned about making the most of every experience, often getting my employees to feel the same way was a challenge. My point is there are really a small handful of guys in the field that have the patience , experience, and the personality that will let them go into that space, relax, enjoy, and do the right job..
That's why this type of work most often done incorrectly, or capable homeowners end up doing it themselves..
Typically, center of the span is optimum but load bearing walls above could offset the load point to off center..Regarding the 1/4" space, not uncommon, the bottom plane of the floor joists will not be consistent with the straight plane of the girder, hardwood shims should be installed , we then secure the shims with construction adhesive..
Just another insight into this type of work. Laying on your back, and crawling around a 3' crawl space with a dirt floor for most people is not much fun. Spiders, garbage, and other unpleasant things make it a job that most people want to get done ASAP..
In my early 20s I learned about making the most of every experience, often getting my employees to feel the same way was a challenge. My point is there are really a small handful of guys in the field that have the patience , experience, and the personality that will let them go into that space, relax, enjoy, and do the right job..
That's why this type of work most often done incorrectly, or capable homeowners end up doing it themselves..