That´s true,it does change the wheelbase,but the actual feel of the bike is more dependant on the reach/BB height and also cs lenght.WB as such doesn´t say much about feel of the bike/frame-example:Koxx sky 2 vs echo pure -1100mm vs 1085mm WB but echo with the same parts will feel longer/more roomy because it has longer reach(660 vs 665mm) even though based on WB you would expect exactly opposite.So if you want your bike to feel longer,I´m affraid your only option is bars(you have already long stem)or maybe shorter cranks(they look like 170mm,not sure of course about this) but I don´t think that´s very good idea either as you would sacrifice some power.