IIRC Optima used the same main frame for 20/26, 20/20* and 26/26 variants of their bikes, simply fitting different forks to suit the front wheel and adjusting geometry using the rear shock mounting. I have the 26/26 version (the Orca) which is very comfortable and stable. Heavy though. At that price, I'd be tempted if it was local, just to see if I'd benefit from the lower front end.
*I'm less sure about 20/20 - the rim brakes are placed for 559 rims on the rear swing arm, so maybe that was swapped too.