I do not believe this mouthfeel thing. I have tried it and could not detect anything at a blind A/B test. I do not remember the exact oat amount, but it was at least 20% of the grist, rest pale malt. The B version was 100% pale. Scott Janish also wrote about it later and pretty much also confirms that this mouthfeel thing only comes into play at amounts above 30%, which are detrimental to the head formation, so not advisable. For starters though, no problem. Starters would be best with 100% oats, but that is a bit... well, hard to handle.
I also could not detect a taste difference btw... But as
@Northern_Brewer keeps saying that it really disurbs him when oats are in the beer, I am thinking that there was maybe something wrong with the test? Don't know. I will brew a pale bitter or mild on Sunday which will contain 10% oats and bittering hops only. So if I can taste the oats in a beer, I should taste it there.