I have build the rv4 and enjoyed it. However, I wouldn't build it again because the flying characteristics disappoint me. The fuse is very wide so you need a long prop to get enough air pass alongside the fuse. The plane is very overbuild wich makes it heavy, I didnt do anything about it because I thought I would be ok.
That plane with a saito 80 is going to be very heavy, I would go for a two stroke, just to save some weight.
That abs cowl sucks, mine broke recently, I you want to get it strong you need to reinforce the inside with fg (which I did), overall that adds quite some weight. The abs wingtips are pretty useless, I didnt use them, instead I used wooden tips, lots better, nicer finish.
I didnt use flaps cause you don't need them, but since you are going to use a heavy engine they might come in handy.
If I were you I would get that SE, just for the better flying characteristics, afterall, that is still more important than looks.
So why did I build it then, well I was doubting between the GP decathlon and the RV, I prefered low wing in the end so I went for it.
Sig isnt available out here, otherwise I would have build a 4*
I'm not trying to talk you out of this, just giving some advise.
I do like to fly it, low passes are great, and it looks good too, but aerobatics are pretty bad. Rolls arent axial at all, even though I have the cg quite a bit back.
I use a 40FX, that isnt enough power, I will be buying a new engine next year, I think that with some more power this plane will be much better to fly.

Just trying to give some advice.