None....
A ballhead on a monopod is just a mess. A single axis tilt head (monopod head) is no better than leaning the monopod over a bit. I just use an arca clamp as all of my lenses have arca plates permanently attached.

Ball head on a monopod is a nightmare, as said at the most all you need is a single axis head. I have one but never bother using it now, just the naked monopod.
http://www.amazon.co.uk/Manfrotto-234-Monopod-Tilt-Head/dp/B000KHZ8AA
The Manfrotto 234RC2 really isn't suitable for larger lenses. According to Manfrotto it's only rated at 2.5kg load capacity. Personally I wouldn't feel comfortable even trusting it with a 70-200mm f/2.8, let alone anything bigger.I have a Manfrotto 234RC2 atop my monopod to allow easy up and down tilting.
I sometimes use a ball head but it's not ideal for bigger/longer lenses - need a monopod head. The little Manfrotto linked above doesn't lock very securely - check out Sunwayfoto, RRS, Hejnar, Custom Brackets.
Hi mark just got a 7d and sigma 150-500 so not a lot at the moment I like the look of the tilt heads they look a lot more controllable its just the price of them Steve
Hi mark I would like on of the rrs mh 01heads as the weight they can support would be good with my dear looks like I will have to do sum saving up for one don't like the ball head on a monopod looks abit hard to control
Steve
The Manfrotto 393 Long Lens Bracket is about £120 I think if you shop around. (or less used)
I know Manfrotto says it was developed for use on a monopod but I've never seen anyone using one that way...
In my mind it just seems like a hassle/mess....but monopods kind of suck anyways.
That RRS head looks strikingly similar to the Sirui I have... to include the crappy delrin (teflon) bearing surfaces/washers.
The problem w/ the delrin is it is "soft" so it has a pretty quick tight/loose transition... It's more like "on/off." And it can hold grit if you are not kind to your equipment (it can get embedded in the teflon).
I'm not very fond of lever clamps because I have a wide variety of plates which vary slightly in size. It can be a problem...
I use it on a monopod (& seen others too)
The OP uses a monopod & is asking for suggestions for wildlife/sport @ not a lot of money.
As far as the delrin goes, I have been able to slacken off the tightness to create a friction setting but as regards whether doing so will wear down the material, I guess only time will tell.
None....
A ballhead on a monopod is just a mess. A single axis tilt head (monopod head) is no better than leaning the monopod over a bit. I just use an arca clamp as all of my lenses have arca plates permanently attached.
Ball head on a monopod is a nightmare, as said at the most all you need is a single axis head. I have one but never bother using it now, just the naked monopod.
http://www.amazon.co.uk/Manfrotto-234-Monopod-Tilt-Head/dp/B000KHZ8AA