I have been pinching motors for a few years. Yes pinching would leave more of a gap between the sleeve and block. The sleeve is strong enough to hold its size without the block's support. I believe some engine manufacturers leave a slight gap on purpose so that when a motor gets hot it doesn't loose all it's pinch. That is why some motors can get over 300 deg and still keep good compression. Pinching is not just a band aid, most motors I have done hold there pinch as long as a new piston and sleeve did, without going through the hassle of a long break in. (I recommend 2 tanks with a re-pinch I have done)
I only charge $15.00 return shipping included, $38 if you send the whole motor. (Usa only for those prices)
www.rw-mods.com

Rex