You have already got some excellent advice by others & glad that you are able to now stitch it perfectly.
19% overlap is surely good enough in most cases, there are times when people have stitched images just with 5-10% overlap with PTGui.
This higher overlap requirement is actually meant for SIFT based programs only as they mostly use the center 50% area of the image to find CP, so 6 shots @ -30 should get you perfect results provided you have other parameters in control. 5 yrs ago I used to do a 360 with 24-70 sigma@24mm & only 5% overlap & it stitched perfectly with pixel peeing details using PTGui.
You can use most of the lenses to do 360 but you would need 1st your hardware calibration for lens+camera & number of shots shooting combination then depending upon the software you use you will need to set certain options in the settings.
Overlap does depend on the amount of details in the so called "featureless" floors & walls but truth is that these floors & walls are seldom featureless, they do have some texture or joints & other patterns but the SIFT alogarithm of APP is not able to detect these low contrast details, the developers of APP are aware of this issue & working on the new v2 of APP which should address this problem, then you will be able to work with lesser overlap.Mediavets reported
From the VRWave.com Panoramic Photography lens database:http://www.vrwave.com/panoramic/photogr
Suggestions/recommendation for Canon EFS 10-20mm wide angle lens are :
1. Min. shots: N, 6 images every 60° at -30° pitch, 6 images every 60° at +30°, Z. Output resolution: 11600 x 5800 pixels - Canon 20D (8mpx)
2. Recommended: N, 4 images every 90° at -60° pitch, 8 images every 45° at 0° pitch, 4 images every 90° at +60° pitch, no zenith image required
3. Alternative: N, 8 images every 45° at -30° pitch, 8 images every 45° at +30° pitch, Z
These 3 suggestions are bcoz different software will have different overlap requirements & the test for any software would be to stitch a low contrast scene with less details & minimum shots from a particular lens.