in my opinion the main challenge with the Su isnt speed, it's actually a very slow flyer due to it's light weight. Videos might make it look faster due to it's small size but in reality it's slow.. The biggest difficulty for anyone with less experience (and for many with lots of experience!) is it's extreme sensitivity to controls. with controls set as per manual with linear movement it's incredibly twitchy and very hard to fly smoothly (or in fact fly at all)
The best way to make the Su more forgiving to fly is to reduce the control throws dramatically.. say 60% or less of recommended values. Then if you have exponential put in abouut 33% expo to soften the control around centre. Once you get used to the model you can increase the throw but even after flying mine fior a while i still find it more pleasant to reduce throws to about 75% of standard values with 33% expo.
Personally I'd not do anything to increase wing area, it's already very lightly loaded and sensitive to any wind when flying outdoors. Increasing wing area will only make the model even more sensitive to wind and will also increase weight thus reducing performance.
Once you are used to the model a brushless conversion is worth considering. as standard the Su doesnt have a lot of surplus power especially after the battery starts depleting (which occurs quickly). A brushless conversion really transforms the model and if you do it with the lightest components you hardly impact flying weight so slow speed handling isnt compomised.