Quoted: I have an Arsenal 105R with way too much trigger slap. Should I send it back to Arsenal? Or is there a better trigger to replace it? Or can I resolve the slap myself with a little modification? Suggestions?

You can contact Arsenal and see if they will replace the set, they have for some people.

If they won't you can try the fix at Linx310's site.  You shouldn't need to cut any tab off your disconnector of an Arsenal FCG though as mine doesn't have one.  That tab is what usually causes trigger slap.  You may just need to change the back lower part of the disconnector profile as marked in blue on the disconnector on his site.  Also consider polishing the FCG while you have it out.

If that won't work you can try a G2 or RSA FCG

Just get the single hook.  The set you have in your SLR-105 should be a milled set and a very good one if you can correct the slap.  The G2 is made from cast metal.  You can always sell the one in your rifle for $30.00 on the Equipment Exchange.