PCP for small frame shooter - with Canadian limitations

Hi Gang! My 7 year old son and I got into PCP air guns last year. We both love shooting pigeons and starlings around the farms we hunt. The only gun we have is a Gen1 Marauder .22. It has the accuracy and power that we need, but its waaay to big for my son to manage. Given his age he's under very direct supervision at all times - I hold the gun on the sticks for him and cover the trigger until he's all set to shoot, then he just shoulders it to aim and when he's ready I take the safety off and he gets to pull the trigger. The darn kid's got the gift of young eyes and he's taken a few pigeons out to 30 yards! But, the stock dimensions are way too large for him and he struggles to get his site picture on steep angled shots (which are the norm). On our last outing, the birds were skittish and a few times he couldn't get settled in fast enough before the flew away - he got pretty frustrated. I don't want that to happen again and ruin his interest.

So, not knowing much about the other PCP options out there I'm looking for suggestions on a more suitable rifle. It must be a PCP, .22 caliber, shoot 1" out to 40 yards and generate 700+ fps. Single load is fine, but a repeater would be better. Being in Canada, we have some silly limitations. 1. we cannot have a pistol over 500 fps, so the Marauder pistol is out (too bad, I really want one). 2. Bullpups are not allowed (I really don't understand why not, as we can own a .223 Tavor bull pup - weird). 

I was thinking of a Discovery and gutting the butt stock down to make it better for my son (would by a maximus but don't think the synthetic stock could be cut down). Any ideas? 
 
well if its like when I was being taught it has a lot to d with weight and the but stock being to long now idk if this would work for you but
http://www.airgundepot.com/hatsan-at44-10-tact-pcp-air-rifle.html
has the AR adjustable style butt stock on it so it can be adjusted to his arms a lot better and with shooting form a stick the weight shouldn't be to much of an issue
or other then it being single shot this might be your better bet
http://www.pyramydair.com/s/m/AirForce_EscapeSS_Air_Rifle_Spin_Loc_Tank/3363
​its light and with the clamp on barrel stock pad thing you can really adjust it for your kid and with the built in power adjuster you can tune can find middle ground on how much power you need to shot count If I had your limitations for my nephew if go with either one of these lucky I don't and he loves his prod
​other then that I cant think of anything other then the Maximus or discovery