Here's my carbine, note take a look at how I mount the rear of my sling to my standard M4 buttstock horizontal slot sling mount (mine shown is not a Boonie Packer sling, it is a more expensive Vickers VCAS two point sling).
I would recommend not using the sling mount under the front sight and under the buttstock, they're just for carrying the carbine and does not work very well for tactical sling use.
You need to get the RRA item # AR0161 side mount sling swivel and mount your sling there and like the one on my picture on the rear slot sling mount on the buttstock.
I also would recommend removing the sling mount under the front sight and under the buttstock, they're not being used so better to remove them from your carbine and also so it won't snag on things.
Plenty of members here recommends the Boonie Packer 2P-TQA 1-1/4" two point sling (you also need to order the optional M4 Kit +$4) priced at $19.95 (with noted M4 Kit grand total of $23.95, this will be my next sling on my RRA 9mm A4 carbine.
http://www.redi-mag.com/index.php?l=product_detail&p=26
Boonie Packer rear sling installation instructions - vid link