Here is what I would do.
Install an o-ring between shroud and barrel band that proves to be fairly tight (I have to push my o-ring in with a little screw driver, I don't have a size off hand) This is easily reversible but I prefer the o-ring in place as it keeps things centered at all times in the barrel band.
-Get a MDS hammer (rocker1 at GTA is a good source, that or jsar) weighing around 50~ grams.
-Research SSG and make one yourself, very easy to do,plan its build into your hammer weight if you do the thru hammer type..its components can be made to save weight if you go that route.
-Maximize hammer throw (measure and reduce valve stem from rear of valve to at least .2", but can go down to .175" very safely unless you run a recessed striker (most dont). This will increase throw minutely but its worth it. Don't forget to shape the edge of the stem like it is in stock form to prevent over flattening from hammer strikes. The alternative to this is recessing your striker or the area your striker makes contact with the valve around .1" into the hammer. (I do a bit of both, my stem protrudes .165" from rear and I recess .03" into hammer, leaving .135" for lift. My gun will never see more than .125" lift so this is fine, however some rifles may need upwards of .15" lift which is why I recommended at least .175" for you)
-Run a valve stem with the area that's in the throat thinned down to around .085~" (from as close as poppet face as you can get to roughly .5" back)
-The above will allow you to run porting of up to .1875" without having to drill out the throat of the valve which is risky. This will require a custom tp that is easy to fabricate from delrin OR order one from Hillairgun. (you can also get poly tubing, cut it to proper length (same length as stock with gaskets installed), heat lightly and stretch over a .1875~ drill bit, repeat until it sets permanently and install) I prefer the delrin rod method as its easy to machine / work with, and doesn't expand/contract like poly tubing, but I've used tubing with success.
-Reduce Poppet OD" from .34" to around .3". Chuck in a drill and lightly run it across sand paper on a flat surface until .3"~ is reached. (this puts less force on the poppet when closed which requires less hammer energy to operate)
-Buy the light valve spring from HillAirGun or source one that is roughly 6-10 lbs as opposed to the stocker that is in the neighborhood of 30 lbs.
-Remove lawyer spring from trigger if you haven't already.
The above mods, provided you DIY, will cost VERY little (20-40$) and take your rifle from ehhh to ahhhh, with impressive gains in both power and efficiency.
As someone else mentioned, if you can afford one, get the aluminum tube to shave around 1.5 lbs off the rifle. (I forget the exact drop, I did this mod before it was commercially available).
I personally have gone above and beyond with my marauder, no regrets as its a tinkerers gun and thats what I enjoy doing, tinkering. I added more plenum volume externally on mine as most in tube regulators have insufficient volume for high power. Reg volume before 20~ cc, reg volume after 53 cc.
And...the max you can take the stock valve safely (imo)..
.234 + .226 / 2 = .23" porting. This was achieved going at a roughly negative 15 degrees towards the rear of the valve to avoid drilling into the valve seat, and safely dremeling the port obligingly until desired results were achieved. The other inhibitor is the barrel ports recessed OD limiting your transfer port od and subsequent porting going through it. Even if you could drill the valve larger than .23", you would have to recess a new transfer port hole into the barrel and valve larger than the current one. The above is extremely hard to achieve and I do not advise attempting it without being willing to ruin a valve or possibly barrel when porting this large in a marauder.
