I have a standard HG70 cassette 13-23 -8speed, and the maximum jump from one cog to the next is 2 teeth. LBS says I cannot have more than 2 teeth jump between cogs. I tried today replacing the 23 cog with a 25, so the jump is 21 to 25 and it works very well.
Will a 19 to 25 jump work? I have a standard SORA triple rear and FD.