May I offer some advice..? Having built a Egli frame, I have been around this matter about rear swing arm spacing and chain-line, and I can have a go at "remembering" how i went about it. First.. the Egli usually has the same swing arm main bearing house dimensions as original, i think to remember the length measure of 168mm. And YES, the arms are NOT symetrical on the main bearing house. That meaning that the LH SWING ARM, IS FURTHER TO THE LEFT. (from the centre line of the bearing housing) BUT this is of less importance, as Trevor said, you are working to get the chain line right. The EGLI spacing should be as the original frame/RFM, from the fact ( i think) that it used the original Vincent rear hub... Here we go: 1, The inside spacing of the RFM, should bee around 225mm. (The same as the rear hub spacing) 2, If you measure from the centre of the rear sprocket, to the inside of the RH "swing arm " this should be 28mm.. 3, If these measures are correct you should measure from inside the RH engine plate, to the centre of the "outgoing engine sprocket" (add a few mill) 4, If you then mark, a point on the swing arm bearing house, that is from the RH side, and the number of millimeter found in point 3, inwards, you have the chain centre line across the bearing house. 5, project a line backwards, and this should end up aprox 28mm inwards from the LH s.arm inside! (remember the measure taken in point 2...) If this ads up everything is OK!! Understand?