also upgraded the harness to
this. before i buy i called to get more info, and found that the simple harness only had 3 d-rings + 1 on crotch. this one has 8 which is plenty i think. plus it has some shoulder pads
D-Rings - With a simple (hogarthian) harness you can move, add or subtract D-Rings wherever (and whenever) you want them. The more complicated harness designs merely add a multitude of D-Rings because they are not flexible to re-locate/adjust the position for the individual user. The Hollis one that you've ordered is a Hogarthian design, but has taken the liberty of pre-installing 2 extra D-Rings on the shoulder straps and the right-side waist band. That's not too bad - the only issue being whether it'd have been cheaper for you to buy a couple of extra metal weight retainers and D-Rings and fitted them yourself.
DIR Compliance - Harnesses which come without a right-side waist D-Ring are created to be 'DIR' compliant. With DIR protocols (as taught by GUE/UTD etc) the diver will carry all of their deco stages on the left-side only. Thus only left-side shoulder and hip D-Rings are needed. The right-shoulder D-Ring exists primarily for clipping off the primary regulator when it is not used. The right-side hip D-Ring is removed/omitted, so that canister lights can be quickly and easily fitted to the right-side waist harness.
Canister Lights - Attaching a canister light is a valid consideration, if you will be progressing to technical/wreck diving. Because the Hollis Solo Harness has a right-side hip D-Ring... and the buckle seems to be (as indicated by the picture in the web link) fitted on the right-side waist belt... adding a canister light to the waist belt would be a royale pain in the butt.
Stage Cylinder Attachment - Other technical agencies are more flexible about deco bottle attachment - allowing cylinders to be stowed on both sides of the diver. Typically, 'right is rich' and 'left is lean' with respect to deco gas O2%. This is a more straight-forward approach for novice tech divers..and one often continued by those who start out that way. The drawback, as mentioned, being easy canister light stowage at the rear of the right-side waist belt.
No. of D-Rings - Given that most technical/cave divers find that 5 or 6 (
if scootering) D-Rings are more than adequate for complex multi-tank deco/overhead dives, I often ponder why recreational divers place such a high value on the existence of a spectacular amount of D-Ring attachments. I think this is a product of scuba industry marketing nonsense - adding extraneous D-Rings is a cheap and brainless way to 'upgrade' the specifications of an otherwise uninspired BCD design - providing that the marketing whizz-kids can paint sufficient gloss on the 'value' of that. The end result being that divers are encouraged to value, and make use of, all these attachment points.... which is the fast-track route to becoming the infamous 'Christmas Tree Diver'.
D-Rings for Stowage - Wanting to avoid the 'Christmas Tree Diver' curse is preferable. Experienced divers don't look upon D-Rings as a means to attach all of their ancillary equipment. For the sake of efficient streamlining, reduced task loading and decreased risk of entanglement - the ideal stowage location for most items is in thigh pockets. Obviously, stage/deco cylinders are stowed on the hip/shoulder D-Rings. When divers use a back-up torch, seeking quick and efficient deployment, they will clip it a shoulder D-Ring...and secure it to the harness with bungee loops to prevent dangling. A rear D-Ring on the crotch strap is often used to secure reels/DSMBs. It can also be used to store extra deco/stage cylinders (tail-dragged). The front crotch-strap D-Ring is never used for stowage - it is for scootering only. Anything attached there is obviously going to dangle well below the diver.
Shoulder Pads - These are only beneficial if you envision you'll be walking long distances on land prior to your water entry. They make no difference underwater (because you're not bearing any weight). The downside is that they can add a little buoyancy (if foam/neoprene) and reduce flexibility to re-position the D-Rings (hence, Hollis have had to add extra ones pre-positioned).
. There nice to have. my [-]current[/-] old bcd had crappy ones. 
