I'll start off by saying I've only been working on full-deck tricks since mid December, mentalism for a few weeks, cups and balls for 5 weeks and had a nice 3-card trick (not a monte type thing) on the go since November.
In short, I'm very much a beginner.
I'm terrible at mental arithmetic. No matter what I tried, I could never remember my times tables at school, I frequently switch numbers around (I'll read 251 as 521, for example) and generally struggle (strange considering I did A-Level maths!).
While you set up the Si Stebbins stack, you go through the pattern so many times that after a couple of practice runs, you'll be at a point where you could technically perform it (of course, the presentation takes more polish, but still). Handled properly - and that's no challenge - it's instant-reset and always ready to go.
Anyway.
I've got a deck set up as Si Stebbins and it's always in my pocket. I've got a routine where I can twice "read" a chosen card while the spec concentrates on it - with a different approach that could go up to 3 or more reads - and I'm working on an extension where they "read" a card of my choosing with the option of going to a Brainwave deck as backup or an add on depending on how well I can perform the transmission bit.
As for people spotting the stack...
My girlfriend is my crash-test-dummy for my magic tricks. When I used the Si Stebbins deck on her she got me to repeat the basic trick something like 8 times on the trot. Each time I did the effect, I spread the cards, used the same moves, took the same glimpse and she couldn't see what was going on.
In the past she's sussed moves in one or two run-throughs, told me where I was flashing palms and so on... this one had her. She's no magician, doesn't want to know how the tricks work but also knows there's something to it.
Oh, she knows about glimpses too. When she was a nipper she learned a trick that uses one and has busted me glimpsing on another effect.
If my girlfriend, a girl who can shuffle, turn down and memorise an entire deck of cards, can't see the stack, I'd be confident spreading the cards in front of anyone.
Yes, the Stebbins stack goes Red Black Red Black all the way through, but to be brutally honest, I don't think real people (as opposed to the kind of nutters, me included, who spend half their free time learning to pretend to have magical powers 

) really pay that much attention. Not even people who know you're up to something and want to catch you. If you're worried, don't leave the spread out there for a 5 minute inspection, just show there's a full set of cards and they'll be happy. I don't say anything, just spread and show the cards. If they think you're memorising the order or something, false shuffle and do the trick without a spread.
A while back I saw a thread where someone said "don't run when you're not being chased"... a point worth keeping in mind here.
When I get around to it, I'll probably learn a deck-switch of some sort so if someone does spot the stack and asks to shuffle it I'll hand them another deck, get them to shuffle it and switch the stacked one back in after. I'm in no hurry to learn that though.
So in summary, I'd suggest setting up a Si Stebbins deck and having a play with it. It'll take you about 5 minutes to set it up from a shuffled deck, quicker from a new one, and have enough dry runs to be able to use it.
Used as a "spec picks a card and you tell them what it is" thing there's really no great feat of memory involved. You just glimpse, employ the incredibly simple system and you've got it. For memorising the positions of cards it will take a bit more effort, I imagine, but noone but the most eagle-eyed of people will spot that the deck is stacked if you spread them face up as you start the effect.
I dunno if this post will help matters, as in some ways I've just repeated what others have said, but maybe the inept handling of new effects my signature alludes to combined with the success I had on first my run through with someone who knows what glimpses are and that I really don't have magical powers will add a bit of context.
All the best. 
