I haven't achieved MB or any classification but as I consider myself fairly knowledgeable in sports training and the like here is my inclination:
You want to combine all the elements which contribute to your performance without any of them competing with eachother and throwing the other off. I would consider the main elements:
Cardiovascular Fitness
GPP - General Physical Preparedness
Strength and Conditioning - which links in with GPP
All of this letterheaded with Diet.
Why?
It has been proven by numerous studies that athletes in ANY field or persuit who are fitter and live a healthier lifestyle tend to perform better than others. Be it curling, sprinting, Judo etc. people with a higher general fitness, better lifestyle and a more natural bodyfat percentage performed better.
So, cardiovascular:
You need a combination of Aerobic and Anaerobic - this means running for distance and at pace. Best option is to run say 1.5 miles, walk briskly for half a mile and then sprint 100m, walk 100metre, sprint etc. for a further mile.
You can obviously scale down the 1.5 miles to a mile which you may find more realistic.
Other option is one day a week run for distance, one day do intervals, one day run for pace but I personally find this a little dull.
Cycling is good as well, get the body working, rowing is great for fitness and GPP.
GPP/Strength:
GPP is basically your ability to carry out general tasks and under this strength can come too.
For GPP you can do things like tossing sandbags, bodyweight squats and pistols, stretchy band expansions, curls, pulls etc, bullworker. Focusing mainly on circuits, continual exercise at a high volume.
Strength wise exercises like pressups and situps are rather ineffective because you don't have enough resistance to really build. However these are great exercises for GPP because they tend to build up the endurance and active ability (which is why the military love them).
Strength in archery probably one to two full body workouts a week depending on what you can take, lots of
compound exercises like Deadlifts, bench etc. in a fairly low rep scheme like 6x4, 5x5 switching to 3x8 on a periodic basis to alter your muscular focus.
For archery I'd personally say doing high reps of things like Pressups, chins and other bodyweight natural motions is probably best - using a rucksack for extra resistance. Search the Thug Workout on youtube - good example.
Diet
This is the crux of it all - basically you want to cut out the big heavy meals so typical these days for 5 - 6 smaller more concise meals. Easier to digest and you can eat more.
Your basic nutritional requirements are Vitamins, Minerals, Protein and Carbohydrate.
Vitamin wise you need to eat fruit and veg on a regular basis. This is easily done, protein you get mainly from meats ie. Tuna, Beef etc. and carbohydrate comes in simple and complex form which you get from sugars and pulses respectively.
To split up your day:
Breakfast
"Snack"
Lunch
"Snack"
Dinner
Optional Extra meal
Breaky - meusli, porridge etc. Lots of complex carbohydrate
Snack 1 - Pasta/Rice with Veg, piece of fruit, peanut butter sandwich etc.
Lunch - Usual type of thing but with a piece of fruit and bigger portions. Bread will provide a lot of complex carbs, anything in the sandwich, other thigns.
Snack 2 - More things like pasta/potato/rice... fruit, veg and all that jazz
Dinner as usual.
You get the idea
And in all this you want to combine a sufficient volume of arrows at a variety of distances in various conditions to give you the best chance at your shooting. Join in every competitive event you can - get used to the pressure so much that it is routine for you.
Key thing as well - chill time. Make sure you have days to recover, days to have off. If it becomes a trial you will cease to enjoy it and thus cease to perform. Allow at least two rest days in the week where you can do other things and just consider your performance the other days. Breaks it up a bit