I would put it closer to the center pole, maybe 6"-10" away. This will serve the keep the stove away from the sidewalls and also maximize the amount of pipe you have inside the shelter, which means you will get more heat from it. Keeping the stove body and pipe away from the silnylon tent is a real consideration, silnylon is not heat resistant at all and will melt or burn.
As others have said, I think a stove, even in small one is going to be pretty tight in an SL3. You can likely get away with it for a single person and their gear, but I think trying to sleep 2 adults in there with the stove would be pushing it. Stoves eat up space in a shelter quickly. Besides the physical space they take up, when they are burning hot you won't want to be much closer than a foot away. Because the backpacking stoves are small, you end up using small wood, which burns really quickly, so you will likely end up with a pile of sticks inside the shelter so you can continually feed the stove. You can put the wood outside the shelter, but then you have to constantly be opening the door which let's out a lot of your heat. Silnylon shelters don't retain warmth very well anyway, so minimizing door openings helps maximize your warmth inside, Not a deal breaker either, but just another thing to consider.