That works fine. No issues with keeping air in after.
The pad I sleep on at home has 3-4 patches like that and keeps air. Probably have 400 or more nights on it-thermarest trail scout. Sometimes I put uncle lou's stealth straps over and put seal seal around the edge but just seam seal wp works by itself. Just let it cure for 24 hrs.
I do put the seam seal on while it is aired up and you can see it bubble a bit. I think in between bubbles it draws the sealant in. After an hour or so I open the deflate valve.