Arbusers

Today there was a huge arb of 5% on a basket game between Pinnacle and a softbook, but right when i was placing the bet at the softbook the line disappeared. It was a handicap +16.5, -16.5. But then i noticed another line for -17.5 which seemed to be off. Unfortunately +16.5 was the maximum pinnacle was offering, so there was no way to arb it, but it made me think if there's any value and is worth taking +16.5, -17.5, the odds for them being 1.775 and 2.75.
I did not place any bet as i didn't have enough time to do the calculations but later i have come to the conclusion that the correct price for -17.5 was around 2.45 (considering pinnacle's odds are right) so the value would be around 4.6%. I know there is risk involved and is not an arb, but since $ is my goal, should i pass this?

It is called "Polish middels": http://analyticalsports.blogspot.com/2007/07/polish-middles.html
Personaly i don't play it yet, but it may be profitable in the long run if you do it correctly.

We can think of this as a straight bet that pays 1.0787 when we win. In general the push-probabilitity for a given spread is less than 5%. This can be inferred from the Pinnacle prices when the spread varies by one point.
So we can expect to win here at least 95% of the time so there is value on your "semi-arb" strategy.