I took the same route as hanleyfan.
I sold my accurate .22 marauder due to it's weight/balance during extended offhanded shotting sessions. I bought a refurbed .22 Disco for under $200, and outfitted it with a BNM Custom Airguns
breech and shroud (same as Discos-R-Us), plus his hammer spring/degasser power adjuster, and a Discos-R-Us
The Disco is actually simpler for a back and forth use for Co2 & HPA, as it has only one adjustment to worry about, the hammer spring. M-rod has 3: hammer spring, hammer stroke, and adjustable transfer port. Also, the Disco is a 2K hpa fill (@135 cc's)vs. the 3K of the M-rod (@215cc's), so you'll get more fills from your scuba tank, and bulk Co2. If you find your air capacity is lacking, there is a double tube kit also available from Airgun Labs
, that will double your air, and still keep the weight down.
Quantum unkown caveat: Crosman is releasing a revised, lighter Marauder in a month or 2. Published M-rod weight is 7.15lbs, mine actually weighed 8.6lbs(unscoped), so YMMV.