Looking at that peashooter, I would not worry too much, it looks like it won't be bothered too much with an additional 500 grammes.

My Seagull FW190A has the ASP radial, which weighs in at near 2,8 kilo. The plane turned out to be built such, that had I fitted a lightweight 40 or 50 cc gasser 2-stroke I would have had to add lead to the nose anyway, as it balanced perfectly with the radial on. So the plane would have ended up exactly at the same weight regardless of a lighter engine.

Then again, you can push forward the decision of which engine, after you have your hands on the plane, right?

As for those aftermarket intake mods offered, I am always a bit suspicious, because usually there are way easier and cheaper options.
My ASP also had a TERRIBLE fuel distribution, and I solved it by simply drilling 3 holes 0,8 mm in the intake elbow. The mod is basically free (OK... a drill bit set including 0,8 mm costs maybe €3,50) but the trick is to know where and how to drill...



Fixed it right up, from this:

to this:

The difference might not be all that audible, but it is not just 4~500 RPM more, it also is a throttle that responds over the full stroke and much more equal cylinder temperatures.
What basically happened was that fuel distribution would vary with throttle opening, so from about half throttle, cylinders that were rich to begin with would go lean and vice versa, resulting in basically no change of RPM, but a lot of change in temperature.
Before the mod, I saw differences in cylinder temperature of 80~100 deg C, after the mod, that reduced to 40 or less. Also, the oil residue from the crankcase cleared up noticably.

Sometimes, people think too much in terms of "I've got a lathe and machining skills", and not enough in terms of "what could be the actual problem"