I Don't use a Ransom rest, but I do benchrest handgun ammo with an inexpensive MTM caseguard rest and it works. The one Midway sells will allow you to dial in the exact pistol height for this purpose. Both are plastic and the MTM will flex a little. 20 rounds in pistol sounds good to me and when you have a load you really feel should be accurate with some past experience with the same bullet and powder, 50 rounds is not a risky proposition considering that it's just not that hard to duplicate factory performance. Especially when using powders that are very well suited to a particular cartridge. In Rifle, 15 or 20 rounds is a good range depending on how many groups you want to fire until you find a majic load. Then again I load a little out of the norm for handguns and carry over rifle principles like high load density into my handgun ammo. For defensive pistol cartridges, I use low flash ball powders that will fill the case as high as possible and the results have been very rewarding.
Loaded some .40 yesterday with 165 gr. Golden Sabers and had planned to use VV 3N37 for low flash/good velocity, but since the expander in my RCBS dies seem better suited for Cast lead, I couldn't get enough tension on the bullet to suit me as the driving band on GS's is the only part of the bullet that is full diameter. Solution; well not exactly since these loads won't likely be suitable as defense loads, but I switched to AA #9 that will fill the case to a level of slight compression and the GS can't go anywhere now but forward. Have not tried this load combo before, so I am expecting a little more flash than a defense load should have. But Hey, may make a great high velocity field load in the 5" barrel of the XD Tactical, so I loaded 100!