Short answer: 10 sounds good.
Since the data is coming from a user input on a filter page I was going to limit the range based on their selections. Having said that, the number of rectangles will flux but not beyond what is legible. Once I begin layout I will be able to better determine those limits.
I'm attaching db3 which should open and show a chart along the lines of what I understand you would like.
The Y-axis is set to '2007' and X-axis set to 0-25 Startpoints, whatever they are. There is no error handling or data verification
Some of your projects only have 2 days between start and finish date so they appear as very slim boxes at this scaling but the purpose of this is a testbed for ideas. You can add additional data rows manually through the subform on the chart. The exact locations of the 'boxes' need adjusting by a line width or so but this is not a final solution.
By making the 'boxes' on the chart TextBoxes they can receive focus so you could click on them to initiate other actions. If the box is too slim to read the text inside the box then you can use the Shift+F2 Zoom function. There is another form purely to manually add "Project Titles"
The chart is based on a local table from which you would have to delete data prior to re-populating with your real data. You would then have to run a loop to number the rows 1 thro 10, unless you handled this in append query.
Please let me know if this has been of any use.
S7