Personally...I think I would try the spray adhesive on an section of a Tshirt that won't be included and see how it looked. You know from having made one already what to expect. If it holds up while you are sewing it together I think that would be fine...once it is quilted it will be stabilized more.
Some of my iron-on stabilizer was loose by the time I got the sewing done. If it doesn't look right...then sell what you have left on here and get what you need.