I did the frame this way because I thought it would give me the best strength while still getting full travel of the gantry rails. The join between the cross rail and foot plate is fully welded and should be very strong.
The bearing blocks are mounted below the "foot" plate. The bmp from my cad drawing below shows how the blocks will be fitted. The top cross bars are not shown here but they will add more strength for left/right forces. The position for the ballscrews is shown as well. These will be covered as well to try to prevent swarf getting to them.

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Name:	Frame.bmp 
Views:	451 
Size:	2.60 MB 
ID:	13157