New K-5 IIs, Sigma lens, and lightroom question

So, I have my K-5 IIs with the Sigma 17-50 F2.8 EX DC HSM. There is an awful lot to learn.
Using Lightroom 4.2
1) testing with DNG+JPG and PEF+JPG seems that DNGs render slower than PEFs.
2) Checking lens profile for the raw files selects the Adobe(Sigma 17-50 F2.8 EX DC HSM Pentax) profile. Great! But doing the same for the JPG files only selects Sigma DG 12-24 F4.5-5.6 EX HSM profile. The correct lens is not listed in the drop-down list. So, am I not to use the lens profile for JPGs or is this a problem?

Should this be addressed in a Lightroom or Lens forum Open Talk)?
Thanks, I appreciate any comments.

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-Richard
Pentax K-5 IIs, Sigma 17-50 F2.8, LX3, Pentax MX w/40-80 & 80-200 lenses, Lightroom 4.2, CS5