Sarge, I'm curious as to what your current all round west coast gun is?
I have also been thinking about a cave/reef/gulley gun. The Foxy Bros. & Gunernsey spearos are a major influence these days, so their enthusiasm for airguns has piqued my interest too. Although, I must admit, I feel a strong affinity for band guns -- just love the simplicity of them (I'm sure archers would understand this).
I have a SeacSub apnea catalog next to me. It features Single & Dual Power Asso pneumatics (the muzzle looks remarkably like the Mambas). They are available in sizes inc. 30cm, 40cm, 55.5cm (the 50), 69cm (the 65) and 79cm (the 75), 90, 115 and 135cm. If they interest you, you might want to look at the DOrset 2006 thread, somebody mentioned using a 50cm Asso.
I am also thinking about something like a 60cm Cressi Commanche, possibly with a trident (Spaghetti recently explained how he uses one as his cave gun in poor viz conditions, rather than the usual pneumatic, so it can become the main gun if viz gets very bad). The fish here in the UK are relatively small & I believe tridents are supposed to be more likely to stun the fish and so reduce tangling. The trident vs. Tahiatian tip is discussed in detail in earlier threads - so I won't do it again here.
I also have an Omer catalog next to me, it features a pneumatic called the Tempest (40/50/70 with or without power regulator) and also the band powered Dragon Cave CM60 (item C602C) & the band powered Excalibur Cave (45/55/65/75) - which both feature trident tips.
Another option: You mention small gun & big spear. The other gun I am considering is a small Rob Allen. Saw a picture of a guy called Pablo with a huge Ling Cod up near Seattle using a 70cm RA railgun with reel (I used to live in the area so it caught my eye [see blottom of page]:
Although 65cm is, I think, currently the smallest size RA advertised, they will still make guns custom lengths to order. I have heard of (and seen pictures of) 50cm Rob Allen guns (see the v. short RA railgun featured on Norcal website's boogey board float project):
http://www.norcalfreedive.com/catalog/tips.php
Rob Allen offer a range of spear diameters (with names like "Stiletto" & "Thunder stick"!) & have I think the knowledge & experience to create a properly balanced gun. Equipped with one or 2x 16mm bulk rubber bands or a single 20mm rubber, depending on your preference. You can opted for a breakaway rig if you are expecting really big fish or a reel if that floats your boat.
